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PU"-M* 


An  Essay 

on  the 

Physiology  of  Mind 

An  Interpretation  Based  on  Biological^ 
Morphological,  Physical  and 
Chemical  Considerations 


BY 

Francis  X./Dercum 

A.M.,  M.D.,  Ph.D. 

Member  of  the  American  Philosophical  Society;   Fellow  of  the 

College  of  Physicians  of  Philadelphia;  Member  of  the  Academy 

of  Natural  Sciences  of  Philadelphia;  Professor  of  Nervous  and 

Mental  Diseases  in  the  Jefferson  Medical  College,  etc 


Philadelphia  and  London 

W.    B.    Saunders     Company 

1922 


Copyright,  1922,  by  W.  B.  Saunders  Company 


MADE     IN     U.     S.     A. 

PRESS     OF 
B.     SAUNDERS     COMPANY 

PHILADELPHIA 


Biomedical 
Library 

\a)U 

(OX 

11  zz 


This  Essay  is  Reverentially 

Inscribed  to  the  Memory 

of 

JOSEPH  LEIDY 

to  whom  especially  we  owe  our 

Knowledge  of  the  Behavior 

of  the 

Rhizopoda 


577957 

i 


FOREWORD 


In  this  essay  the  writer  has  endeavored  to 
present  the  basic  facts  of  those  reactions  of  the 
organism  to  the  environment  which  under 
given  conditions  manifest  the  qualities  which 
we  speak  of  as  "mind."  As  far  as  possible 
elemental  truths  have  been  sought  in  a  con- 
sideration of  the  structure  of  the  constituent 
substance  of  the  organism,  the  living  proto- 
plasm. The  physical  peculiarities  of  the  latter, 
its  ceaseless  chemical  change,  its  simultaneous 
up-building  and  reduction,  its  reactions  and 
its  lack  of  reactions  to  the  incident  forces  of  the 
physical  world,  have,  in  turn,  been  called  to  the 
attention  of  the  reader.  Secondly,  the  behavior 
of  simple  unicellular  forms  of  life  has  been 
compared  with  and  in  a  measure  correlated  with 
the  behavior  of  the  individual  cells  of  multi- 
cellular forms. 

In  due  course,  also,  have  been  considered 
those  peculiarities  of  structure  of  the  living 
protoplasm  which  cause  the  arrest  of  certain, 
a  very  limited  number,  of  the  incident  forces 
of  the  environment;  protoplasm  as  a  whole  is 
"transparent"  to  and  remains  totally  unaffected 
by  an  infinitude  of  forces  active  in  the  universe. 

3 


4  FOREWORD 

In  turn  the  writer  has  taken  up  the  problems 
of  the  reception  and  transmission  of  the  forms 
of  energy  which  protoplasm  is  capable  of  re- 
ceiving, the  conversion  of  these  incident  forces 
into  other  forms,  and  the  transmission  and  the 
release  of  energy  by  the  protoplasm  itself. 
Naturally,  this  discussion  is  preceded  by  a 
consideration  of  elementary  responses  to  im- 
pacts, by  a  consideration  of  the  differentiation 
in  metazoa  of  special  structures  for  the  recep- 
tion and  transmission  of  the  latter,  and  for  the 
resulting  expression  in  motion;  and,  finally,  by  a 
consideration  of  the  elaboration  and  differentia- 
tion of  these  phenomena  in  the  more  complex 
metazoa. 

At  first  the  responses  of  the  organism  are 
very  general  in  character.  Soon,  however, 
they  become  limited  and  special,  and  later 
acquire  the  character  of  being  fixed,  stereotyped, 
and  invariable.  Later  still,  owing  to  an  increase 
— an  increase  which  finally  becomes  vast — 
in  the  number  of  the  integers  concerned  in 
transmission  and  owing  to  the  preservation  in 
these  integers  of  certain  primitive  and  undiffer- 
entiated properties,  the  responses  lose  this 
quality  of  fixation.  They  become  capable  of 
variation  and  acquire  the  quality  of  being  more 
and  more  adaptable  and  adjustable  to  the 
impacts  received;  the  responses  become  more 


FOREWORD  5 

and  more  the  exact  or,  rather,  the  increasingly- 
approximate  equivalents  of  the  impacts. 

The  recondite  problems  of  consciousness  now 
present  themselves  and  its  elemental  phenomena 
first  occupy  our  attention.  Finally,  the  writer 
directs  attention  to  some  of  the  remarkable 
physical  facts  definitely  known  in  regard  to  the 
responses  of  the  organism,  facts  which  possess. 
a  profound  significance  and  which  must  pro- 
foundly influence  our  conceptions  both  of  the 
structure  of  protoplasm  and  of  the  limitations 
which  this  structure  imposes.  Here  appears 
the  great  question:  "What  and  how  much 
does  our  structure  permit  us  to  know?" 

In  conclusion  the  writer  wishes  to  say  for  the 
lay  reader  into  whose  hands  this  essay  may  fall, 
that  as  far  as  practicable  the  language  employed 
has  been  as  simple  as  the  nature  of  the  subject 
permits.  Unfortunately,  however,  many  tech- 
nicalities are  unavoidable,  though,  whenever 
possible,  the  meaning  of  these  has  been  indicated 
in  the  text. 

F.  X.  D. 

1719  Walnut  Street, 

Philadelphia,  Pa. 

January,  1922. 


CONTENTS 


PAGE 

Attitude  Toward  the  Subject 11 

Reactions  of  Unicellular  Forms  and  of  the  Individual 

Cells  of  Multicellular  Forms 12 

Primitive  Responses  of  Movement  in  Multicellular 

Forms 15 

Differentiation  of  a  Contractile  Cell 16 

Transmission  of  Impacts 19 

Primitive  Pathways  of  Transmission 21 

Differentiation  of  a  Receiving  Cell 23 

Differentiation  of  an  Intermediate  Cell 24 

Position  of  the  Primitive  Transmitting  Apparatus. 
Position  Later  Assumed  in  the  More   Complex 

Metazoa 24 

Structure  of  the  Primitive  Transmitting  (Nervous) 

Network 26 

Differentiation  of  a  Synaptic  Nervous  System 27 

The  Neurone 28 

Polarity  of  Transmission 30 

Mechanism  of  Response 31 

Differentiation  of  Responses 33 

Impacts   Which   Living   Protoplasm   is   Capable   of 

Receiving 34 

Chemical  Impacts 34 

Impacts  from  Movements  and  Coarse  Vibrations  in 

the  Surrounding  Medium 35 

The  Otic  Vesicle,  the  Ear,  the  Lateral  Line 35 

Impacts  of  Light,  of  Heat 37 

Limited  Capacity  of  Living  Protoplasm '  for  the 
Reception  of  the  Incident  Forces  of  the  Environ- 
ment.    Significance  of  this  Fact 39 

Differentiation  of  the  Receptors.    Physical  Character 

of  their  Function -. 42 

7 


8  CONTENTS 


P.VGB 


Methods  of  Response  by  the  Organism 47 

Establishment  of  Definite  Pathways  of  Transmission. 

The  "Common  Paths" 48 

Segmental  Relations  of  the  Central  Nervous  Appa- 
ratus       49 

Segmental  Relations  of  the  Cephalic  Extremity  and 

the  Special  Sense  Receptors 50 

The  Nose  Brain,  Eye  Brain,  Ear  Brain,  Skin  Brain, 

Visceral  Brain 50 

The  Chemical  Sense.     Automatism  of  Response  in 
the   Approach   to   or   Withdrawal   from   Foreign 

Bodies 51 

Roles  of  the  Other  Senses 54 

Automatic  Character  of  the  Spinal  Responses 55 

The  Palseo-encephalon;  the  Brain  Stem;  Responses 

Fixed,  Invariable 56 

The  Neo-  or  Telencephalon;  the  Cortex;  Responses 

Variable  and  Adaptable 57 

Absence  of  Segmental  Relations  of  the  Telencephalon     57 
Pathways  of  Ingress  and  Egress  to  the  Telencephalon    58 
Functions  of  the  Cortex;  the  So-called  Centers.    As- 
sociation Pathways.    Relation  of  the  Various  Parts 
of  the   Cortex   to   Each   Other.     Possibilities   of 

Adaptation  and  Adjustment  of  Responses 60 

The  Responses  of  the   Cortex  Being  Variable  the 
Neurones  Cannot  Be  in  Fixed  Relations  with  Each 

Other 62 

Amoeboidism  of  Cortical  Neurones;  Historical  Data. 

Discussion 63 

The  Neuroblast.     Chemotaxis;  Neurobio taxis 67 

The  Synapses.     Polarization  of  the  Neurone 70 

Further  Discussion  of  the  Amoeboidism  of  the  Neurone     71 

Synaptic  Delay 72 

The  Electro-endosmotic  Layer 74 

Amoeboid  Transmission.     The  Neurone  Threshold. . .     78 


CONTENTS  9 


PAGE 


The  Principles  that  Determine  Neurobiotaxis  and  the 
Principles  that  Determine  the  Direction  of  Trans- 
mission.    Old  and  New  Pathways  of  Transmission     79 

Changes  in  the  Neurone.  Release  of  Energy.  Ava- 
lanche Conduction 81 

Consciousness.  Sentiency.  The  Lower  Forms  of 
Life;  the  Lower  Vertebrates;  the  Higher  Verte- 
brates. The  Role  of  the  Pallium;  the  Role  of  the 
Palseo-encephalon 83 

In  Mammals  Fixed  Responses  Play  no  Role  in 
Consciousness 86 

Disappearance  of  Consciousness  in  Acquired  Autom- 
atisms      87 

Consciousness  Present  Only  in  Responses  of  Adapta- 
tion and  Adjustment 88 

Phenomena  of  Transmission  Through  the  Cortex. 
Relations  of  These  Phenomena  to  Consciousness. . .     89 

Nature  of  Consciousness 90 

Principles  that  Govern  Transmission 93 

The  Train  of  Activity.  The  Field  of  Consciousness. 
Community  of  Consciousness,  Sense  of  Self 95 

Memory;  its  Automatism.     Instincts 96 

Perception;  Apperception;  Thought 99 

The  Conscious  and  the  Unconscious  Fields.  Physi- 
ology of  the  Latter 101 

The  Re-forming  of  Old  and  the  Formation  of  New 
Combinations  Among  the  Neurones;  Originality; 
Imagination 103 

Relative  Dynamic  Power  of  the  Conscious  and  Un- 
conscious Fields.  Dynamic  Levels.  Attention; 
Concentration;  Initiative;  Will  Power 105 

Sentiency.     Sensation.     Role  of  the  Telencephalon. .   106 

Special  Sensations  Derived  from  Physical  Impacts. 
Extero-,  Intero-,  and  Proprioceptors.  Pleasure, 
Pain.     The  Emotions;  Affects 107 


10  CONTENTS 


PAGE 


Physical  Conceptions  in  the  Interpretation  of  Mind  114 

Significance  of  the  Element  of  Time 115 

Significance  of  Weber's  Law 116 

Inferences  as  to  the  Changes  in  the  Structure  of 
Protoplasm  in  Response  to  Changes  in  the  Outside 

World 118 

Limitations  of  Possibilities : 

a,  Only  Such  Changes  as  Protoplasm  is  Capable  of 
Receiving; 

b,  These  Changes  Correspond  Only  Imperfectly 

to  Changes  in  the  Outside  World 119 

Memory    Pictures;    Composite    Pictures;    Abstract 

Conceptions;  Abstract  Thinking;  Dangers 120 

Final  Word  as  to  the  Biological  Interpretation  of  Mind : 
Objections  to  the  Greek    Word  (poyj  and  Its 

Derivatives. 
Objections  to  the  Latin  Word  Spiritus  and  Its 
Derivatives 122 

ADDENDUM 

The  Pathological  Physiology  of  Mind 126 

Hysteria,  Hypnosis,  Dreams 127 

Delirium/^Confusion,  Stupor 131 

Hallucinations,  Illusions,  Delusions 132 

Variability  of  Neurone'Relations 133 

The   Biological   Endogenous   Deteriorations.       The 

Precocious  Dementias.    The  Paranoid  States 134 

The*Appearance  and  Significance  of  Fixation 138 

Melancholia,  Mania 139 

Index 143 


AN  ESSAY 

ON   THE 

PHYSIOLOGY   OF  MIND 

An  Interpretation  Based  on  Biological, 
Morphological,  Physical,  and  Chemical 
Considerations 


To  the  writer  it  has  seemed  that  all  of  the 
phenomena  embraced  by  human  experience,  no 
matter  what  their  character,  must  be  approached 
from  the  standpoint  of  cold,  unemotional,  sci- 
entific observation  and  analysis.  This  neces- 
sitates as  a  preliminary  an  attitude  of  mind  in 
which  preconceived  ideas,  prejudices  of  what- 
soever character,  previous  beliefs,  and  concep- 
tions are  set  aside.  In  no  field  is  this  more 
important  that  in  the  study  of  the  phenomena 
embraced  under  the  term  "mind."  Long  the 
subject  of  the  discussions  of  metaphysicians  and 
in  later  times  of  psychologists,  the  phenomena 
of  mind  have  been  approached  as  though  they 

were  altogether  peculiar  in  their  character  and 

11 


12  THE  PHYSIOLOGY  OF  MIND 

being;  as  though  a  difference  essential  and  in- 
trinsic separated  these  phenomena  by  a  wide 
and  hopeless  gap  from  all  other  phenomena  of 
nature.  Let  us  see  whether  such  an  attitude, 
such  a  preconceived  notion,  is  justified. 

When  we  turn  our  attention  to  some  of  the 
lower  forms  of  life,  for  example,  to  the  pro- 
tozoa, and  notably  to  the  simple  expression  of 
life  as  witnessed  in  the  amoeba,  we  find  that  the 
organism  reacts  in  an  already  complex  manner 
to  the  environment;  thus,  when  the  pseudopod 
of  an  amoeba  comes  in  contact  with  a  foreign 
body  one  of  two  things  occurs:  either  the  pro- 
toplasm of  the  pseudopod  flows  around  the  for- 
eign body  and  thus  takes  the  latter  into  the 
interior  of  its  own  substance,  or  the  pseudopod 
is  withdrawn.  Here  we  have  undoubtedly  a 
"selective"  action.  If  the  foreign  substance  is 
capable  of  serving  as  food,  it  is  appropriated;  if 
not,  it  is  rejected.  Should  the  foreign  body  be 
made  up  both  of  material  capable  of  serving  as 
food  and  of  material  incapable  of  serving  such 
a  purpose,  the  two  are  separated;  after  a  time 
the  first  disappears,  apparently  becomes  a  part 
of  the  substance  of  the  amoeba;  the  second  is 
ejected.     No  one,  I  believe,  would  be  so  ven- 


THE  PHYSIOLOGY  OF  MIND  13 

turesome  as  to  interpret  these  phenomena  as 
the  volitional  acts  which  they  so  closely  re- 
semble. Evidently  they  are  merely  the  result 
of  the  physical  (or  physico-chemical)  reaction 
of  the  protoplasm  of  the  amoeba  with  the  ma- 
terial of  the  foreign  body.  Our  increasing  knowl- 
edge of  the  functions  of  the  cells  in  the  higher 
animals  has  taught  us  that  not  only  have  these 
cells  the  special  functions  pertaining  to  the  tis- 
sues of  which  they  are  parts  but  also  that  they 
retain,  in  addition,  the  primordial  property  of 
selecting,  digesting,  and  assimilating  their  own 
food.  It  would  appear  that  the  cells  of  the 
various  tissues  possess  each  a  special  structure, 
a  special  metabolism;  that  is,  each  cell  contains 
special  ferments  by  means  of  which  it  builds 
itself  up,  adds  to  its  own  substance  out  of  the 
general  material  of  the  blood  plasma.  The  cells 
thus  have  the  power  of  "selecting"  foreign 
materials,  of  fragmenting  them,  and  of  utilizing 
them  for  purposes  of  reconstruction  or  as  sources 
of  energy.  The  purely  physical  character  of 
these  changes  are,  of  course,  beyond  question. 
Fats  are  split  into  alcohol  and  fatty  acids;  car- 
bohydrates are  broken  up;  albumin  is  con- 
verted into  peptones;  the  latter  are  split  into 


14  THE  PHYSIOLOGY  OF  MIND 

amino-acids  and  these  again  into  still  simpler 
bodies.     In   turn,   the   cells   give   up   into   the 
blood-stream    substances    so   far   reduced    that 
they  are  no  longer  sources  of  energy,  can  no 
longer  play  a  role  in  the  metabolism  of  the  cell. 
Not  only  have  the  cells  of  multicellular  forms 
retained  the  power  of  selecting,  appropriating, 
and  discarding  the  various  materials  concerned 
in  their  metabolism,  but  such  cells  as  are  not 
fixed  in  the  tissues,  e.  g.,  the  white  corpuscles 
of   the   blood,  have   retained    in   addition   the 
power  of  independent  movements  and  of  act- 
ually extending  and  retracting  portions  of  their 
substance    in    every    way    comparable    to    the 
pseudopods    of    the    amoeba.      Surely    no    one 
would  ascribe  the  action  of  the  individual  cells 
of  the  multicellular  animals  to  volition.     Both 
the  "selective"  action  and  the  power  of  reduc- 
ing the  material  selected  into  components  suit- 
able for  appropriation  into  its  own  substance 
are  properties  inherent  in  living  protoplasm  and 
which  the  tissue  cell  shares  with  the  most  prim- 
itive unicellular  forms.     No  volitional,  no  so- 
called  "psychic"  act  can  be  considered  as  enter- 
ing into  the  phenomena.    It  seems  almost  super- 
fluous to  repeat  that  they  are  clearly  the  result 


THE  PHYSIOLOGY  OF  MIND  15 

of  purely  physical  and  chemical  processes.  They 
merely  instance  the  action  of  colloidal  sub- 
stances upon  each  other  and  upon  other  sub- 
stances; an  action  in  which  the  ions  of  the  con- 
tained crystalloids  no  doubt  also  play  a  part;  in 
short,  the  problem  is  one  of  chemistry,  of  elec- 
tromagnetic or  equivalent  reactions. 

We  have  in  the  selection  and  appropriation  of 
food  by  the  cells  of  the  tissues  an  instance  of 
the  retention  by  the  individual  cells  of  multi- 
cellular organisms  of  the  primitive  properties  of 
the  single  cell  of  unicellular  forms.  When  we 
turn  our  attention  in  multicellular  forms  to 
other  properties  which  have  likewise  to  do  with 
the  reaction  of  the  organism  to  the  environment, 
other  equally  interesting  facts  become  apparent. 
Let  us  begin  with  sponges.  According  to 
Parker,1  "Some  sponges,  such  as  the  Stylatella, 
appear,  when  out  of  water,  to  be  more  or  less 
shrivelled  or  contracted  and  under  other  cir- 
cumstances to  be  plump  and  well  rounded  out. 
The  differences  which,  for  reasons  to  be  men- 
tioned presently,  are  known  not  to  be  due  to 
the  simple  physical  loss  of  fluid,  are  apparently 

1  G.  H.  Parker,  Sc.D.,  "The  Elementary  Nervous  System,"  Phila- 
delphia and  London,  J.  B.  Lippineott  Company,  p.  26. 


16  THE  PHYSIOLOGY  OF  MIND 

dependent  upon  a  general  contractility  of  the 
whole  flesh  of  the  sponge  which,  though  slight, 
may  nevertheless  enable  the  sponge  to  change 
its  form  somewhat."  Again,  the  dermal  mem- 
brane of  sponges  which  is  a  tissue  which  has  not 
become  differentiated  into  cells,  but  remains 
syncytic,  has  the  property  of  closing  the  pores 
of  the  sponge  apparently  by  flowing  over  and 
coalescing,  thus  forming  "over  the  external  end 
of  the  pore  canal  an  extremely  thin  sheet,  the 
pore  membrane,  near  the  middle  of  which  the 
pore  has  disappeared."1  The  movement  of  the 
pore  membrane  "is  hardly  to  be  described  as 
purely  amoeboid.  It  seems  to  represent  a  stage 
of  differentiation  between  amoeboid  motion  and 
simple  muscle  contraction  which  may  well  in- 
dicate the  kind  of  contractility  that  the  com- 
mon flesh  of  the  sponge  possesses."2  In  addi- 
tion, the  pores  may  be  closed  in  some  sponges 
not  only  by  the  formation  of  a  pore  membrane 
but  also  by  the  closure  of  the  canal  leading  to 
the  pore — the  pore  canal — itself.  "This  is  prob- 
ably due,  according  to  Wilson,  to  a  contraction 
of  the  epithelial  lining  in  the  pore  canal  acting 
after  the  fashion  of  a  sphincter."3    The  cells  of 

1  See  Parker,  loc.  cit.,  p.  34.      2  Loc.  cit.,  p.  36.       3  Loc.  eit.,  p.  35. 


THE   PHYSIOLOGY  OF  MIND  17 

this  epithelial  lining  "are  in  every  way  com- 
parable to  a  primitive  form  of  smooth  muscle- 
fiber.  Their  superficial  position  places  them  in 
contact  with  the  water  passing  through  the  canal 
and,  as  they  respond  to  differences  in  this 
water,  they  are  without  doubt  capable  of  direct 
stimulation."  To  repeat,  then,  we  have  in  the 
sponges  not  only  a  general  contractility  of  the 
organism  as  a  whole,  together  with  an  amoeboid 
movement  of  the  dermal  membrane,  but  also  a 
sphincter-like  action  in  the  canals  due  to  spe- 
cialized cells.  The  latter  correspond  to  the 
smooth  muscle  cells  of  other  metazoa.  They 
have,  of  course,  no  nerve  supply  and  are  de- 
pendent for  their  stimulation  to  contraction  on 
the  physical  contact  with  the  changing  water 
and  its  contained  substances. 

It  is  interesting  to  note  that  in  the  higher 
animals  muscle-fibers  still  exist  which  like  these 
primitive  muscle  cells  of  sponges  are  capable  of 
responding  to  direct  physical  stimulation  inde- 
pendently of  any  nervous  influence.  This  has 
been  clearly  demonstrated,  for  instance,  by  a 
number  of  observers  to  be  the  case  in  the  iris. 
In  fishes,  amphibians,  birds  and  mammals,  and 
probably  in  the  eyes  of  cephalopods,  the  sphinc- 


18  THE  PHYSIOLOGY  OF  MIND 

ter  of  the  pupil  may  be  regarded  as  normally 
subject  to  direct  stimulation  by  light,  notwith- 
standing the  fact  that  it  is  also  under  nervous 
control.1  Similarly,  the  vertebrate  heart  mus- 
cle appears  to  be  equally  subject  to  direct  phys- 
ical stimulation.  While  the  adult  heart  is 
abundantly  supplied  with  nerves  and,  indeed, 
itself  contains  an  abundance  of  nerve-cells,  no 
such  facts  obtain,  so  far  as  is  known,  in  regard 
to  the  developing  heart  of  the  embryo.  Indeed, 
in  the  chick  the  heart  appears  in  about  twenty- 
three  hours  of  incubation  and  begins  to  pulsate 
about  six  hours  later,  at  a  time  when  the  neural 
crests  and  neuroblasts  have  not.  yet  been  dif- 
ferentiated. Hence,  there  is  every  reason  to 
believe  that  in  the  beginning  it  is  absolutely 
free  from  possible  nervous  influence  and  that  its 
beat  is  purely  myogenic.2  Many  similar  in- 
stances of  muscle  activity  independent  of  ner- 
vous influence  might  be  cited.  It  is  true  ap- 
parently of  the  heart  of  the  tunicate,  of  the 
muscle-fibers  of  the  amnion  of  the  chick,  and  of 
the  circular  and  acontial  fibers  of  sea-anemones.3 
We  have,  then,  as  one  of  the  primary  facts  of 

1  See  Parker,  loc.  cit.,  pp.  50-53.  2  Loc.  cit.,  pp.  53-56. 

3  Loc.  cit.,  pp.  59-61. 


THE  PHYSIOLOGY  OF  MIND  19 

the  reaction  of  the  organism  to  the  environ- 
ment a  response  in  movement.  This  is  expressed 
in  the  amceba  in  the  movements  of  its  pseudo- 
pods,  and,  in  such  multicellular  forms  as  the 
sponges,  in  the  movements  of  the  syncytic 
dermal  membrane,  in  the  contraction  of  the 
cells  about  the  canals,  and  in  the  movement  of 
the  body  of  the  animal  as  a  whole. 

The  next  question  that  presents  itself  is  as  to 
the  capacity  of  living  protoplasm  for  the  trans- 
mission of  motion  through  its  own  substance. 
It  is  not  my  intention  to  take  up  at  this  point 
the  reaction  of  protoplasm  to  light,  to  heat,  to 
electricity,  or  to  sound,  but  rather  its  reaction 
to  those  more  grossly  mechanical  forces  implied 
by  the  impact  of  foreign  bodies.  In  the  sense 
here  employed  mere  contact  implies  such  an 
impact.  To  begin,  if  transmission  of  a  mechan- 
ical impact  actually  takes  place,  it  would  not  be 
surprising  to  find  that  this  transmission  is  rela- 
tively slow.  Proteins  are  extremely  complex 
compounds.  They  are  made  up  of  many 
amino-acids;  as  many  as  seventeen.  Emil 
Fischer,  it  may  be  recalled,  succeeded  in  com- 
bining as  many  as  nineteen  amino-acids  in  the 
synthetic  construction  of  an  artificial  protein* 


20  THE   PHYSIOLOGY  OF  MIND 

It  is  a  legitimate  inference  from  these  and  other 
facts  that  the  structure  of  living  protoplasm  is 
that  of  an  exceedingly  complex  colloid,  the  dis- 
perse and  continuous  phases  of  which  must 
necessarily  bear  multiple  and  complicated  rela- 
tions of  surface  and  interfacial  tension  and  of 
electrical  charge  to  each  other.  It  would  seem 
that  considerable  time  relatively  must  neces- 
sarily elapse  for  the  diffusion  or  transmission  of 
a  mechanical  impact  through  such  a  substance. 
That  transmission  or  diffusion  takes  place 
from  one  part  of  a  protozoan  to  another  part  as 
a  result  of  impact  or  contact  is  exceedingly 
probable.  In  the  amoeba  the  transmission  ap- 
pears to  be  more  or  less  widely  diffused,  for  not 
only  a  pseudopod  but  the  organism  as  a  whole 
may  move  toward  the  food.  The  diffusion, 
however,  appears  to  be  very  slow.  In  simple 
multicellular  forms  such  as  the  sponges  trans- 
mission likewise  takes  place.  Thus,  Parker 
states1  that  if  a  pin  is  stuck  into  a  finger  of 
Stylatella  at  1^  cm.  from  the  osculum,  the 
osculum  will  close  in  about  ten  minutes;  and 
further,  that  ".the  sluggish  transmission  upon 
which  this  reaction  depends  represents  without 

1  See  Parker,  loc.  cit.,  p.  42. 


THE  PHYSIOLOGY  OF  MIND  21 

doubt  that  elemental  property  of  protoplasmic 
transmission  from  which  true  nervous  activity 
has  been  evolved.  It  may,  therefore,  not  in- 
appropriately be  called  neuroid  transmission."1 
Similarly,  in  other  animals  a  transmission  of 
motion  through  non-active  and  non-nervous 
protoplasmic  tissue  can  be  demonstrated  as 
when  motion  is  transmitted  from  one  field  of 
cilia  to  another,  although  quiescent  or  non- 
ciliated  tissues  lie  between.  According  to 
Parker,  "it  appears  that  the  ordinary  tissues  of 
animals,  at  least  their  ciliated  epithelia,  may 
exhibit  sluggish  forms  of  transmission  that  are 
so  like  those  seen  in  sponges  as  to  admit  of  being 
classed  under  the  single  head  of  neuroid  trans- 
mission."2 

Obviously,  it  is  greatly  to  the  advantage  of 
an  organism  when  special  pathways  for  trans- 
mission are  differentiated.  Such  pathways  make 
their  appearance  in  the  primitive  nervous  appa- 
ratus of  ccelenterates.  This  nervous  apparatus 
has  been  elaborately  studied  in  jelly-fishes  and 
sea-anemones.  In  the  former,  impressions — 
stimuli — upon  the  marginal  bodies  are  diffused 
through   deeper   lying   muscle-cells,   so   that   a 

1  See  Parker,  loc.  cit.,  p.  64.  2  Loc.  cit.,  p.  75. 


22  THE  PHYSIOLOGY  OF  MIND 

contraction  takes  place  in  the  large  circular 
sheet  of  muscle  that  forms  the  sphincter-like 
organ  midway  between  the  centrally  located 
mouth  and  the  edge  of  the  bell.  This  contrac- 
tion reduces  the  cavity  of  the  bell  and  by  thus 
driving  the  water  out  of  this  cavity  forces  the 
animal  forward.1 

In  the  sea-anemones  an  impulse — a  mechan- 
ical stimulus — applied  to  the  surface  of  the  ani- 
mal results  in  a  retraction  of  the  oral  disc. 
Investigations  have  shown  that  the  impulse 
both  in  the  jelly-fish  and  the  sea-anemone  is 
diffused  through  a  well-defined  nervous  net- 
work. When  this  nerve  tissue  is  studied  it  is 
found  to  consist  of  a  diffuse  and  continuous 
network  which  also  contains  cells.  The  fact 
that  the  network  is  continuous  and  diffuse  sug- 
gests an  analogy  to  the  syncytic  tissue  of  the 
dermal  layer  of  the  sponges.  In  keeping,  how- 
ever, with  what  one  would  expect,  the  evolu- 
tion of  special  pathways  for  transmission,  leads 
— judging  by  the  time  of  the  response — to  an 
increased  speed  of  transmission;  the  response, 
which  is  very  slow  in  sponges,  is  much  more 
rapid  in  the  ccelenterates. 

1  See  Parker,  loc.  eit.,  p.  103. 


THE  PHYSIOLOGY   OF  MIND  23 

Let  us  now  turn  our  attention  once  more  to 
the  primitive  muscle-cell  in  the  pore  canals  of 
the  sponges.  This  muscle,  as  we  have  seen,  sug- 
gests the  smooth,  unstriated  muscle-cell  of  the 
higher  animals;  indeed,  such  a  muscle-cell  is 
still  found  in  some  of  the  tissues  of  the  latter 
existing  as  a  prototype  independent  of  nervous 
influence.  A  muscle-cell  independent  of  .ner- 
vous influence  reacts  directly,  as  we  have  seen, 
to  a  stimulus  applied  to  it.  This  is  unques- 
tionably the  case  in  the  muscle-cell  in  the  pore 
canal  of  the  sponge,  in  which  the  stimulus  is 
the  flowing  water  and  the  substances  contained 
in  the  latter;  similar  facts  obtain  in  the  case  of 
the  other  independent  smooth  muscle-cells  that 
have  been  instanced.  In  the  sea-anemones  and 
the  jelly-fishes,  however,  the  muscle-cell  no 
longer  receives  its  stimulus  directly  from  the 
environment.  There  is  now  interposed  an  epi- 
thelial cell  which  receives  the  stimulus  and 
transmits  it  to  the  muscle-cell.  This  epithelial 
receiving  cell  acts  as  a  "sense"  cell  and  is 
termed  the  "receptor,"  while  the  muscle-cell  to 
which  it  conveys  the  stimulus  is  known  as  the 
'  'effector. ' '  Later  a  third  structure  appears  inter- 
posed between  the  receiving  cell  and  the  muscle- 


24  THE   PHYSIOLOGY  OF  MIND 

cell.  The  function  of  the  new  structure,  a  cell 
termed  by  Parker  "protoneurone,"  appears  to 
be  to  diffuse  and  to  distribute  to  the  muscle- 
cell  or  cells  the  stimulus  derived  from  the  re- 
ceiving cell.  Its  function  is  that  of  an  inter- 
mediary. Evidently  we  have  presented  here  an 
arrangement  which  is  the  prototype  of  the 
sensory,  nervous,  and  muscular  system  of  the 
higher  animals. 

Certain  other  important  considerations  now 
present  themselves.  In  the  higher  animals  the 
nervous  system,  which  in  sea-anemones  and 
jelly-fishes  is  largely  superficial,  existing  in  the 
epithelial  layers  of  the  animal,  becomes  grad- 
ually more  and  more  deeply  seated  and  better 
protected.  This  is  seen  in  the  higher  inver- 
tebrates and  vertebrates  alike.  In  invertebrates 
there  is  a  gradual  retreat,  a  migration,  of  the 
nervous  apparatus  into  the  interior  of  the  ani- 
mal; in  vertebrates,  as  evidenced  by  embry- 
ology, a  portion  of  the  epidermal  layer,  a  por- 
tion doubtless  corresponding  to  a  primitive  area 
of  receptor  or  sensory  epithelium,  becomes 
grooved  and  finally  inclosed  by  the  infolding  of 
the  edges  of  the  groove. 

Interesting  as   these  facts   are,   a   still    more 


THE  PHYSIOLOGY  OF  MIND  25 

important  consideration  remains.  The  nervous 
system  of  ccelenterates,  as  we  have  pointed  out> 
consists  of  a  diffuse  and  continuous  network 
which  also  contains  cells  and  which  is  grossly 
analogous  to  the  syncytic  tissue  of  the  dermal 
layer  of  sponges.  Restating  the  facts  thus  far 
considered,  we  find  that  the  most  elemental 
form  of  response  by  an  organism  to  the  en- 
vironment— next  to  the  movement  of  the  pseu- 
dopod  of  an  amoeba — consists  in  the  contraction 
of  an  epithelial  cell,  a  cell  analogous  to  a  smooth 
muscle-cell,  directly  in  response  to  a  stimulus. 
The  next  stage  consists,  as  also  pointed  out,  in 
the  appearance  of  another  epithelial  cell  which 
does  not  itself  contract,  but  receives  the  im- 
pression or  stimulus  and  transmits  it  to  the 
contractile  cell.  In  this  primitive  arrangement 
the  first  or  receiving  cell,  the  receptor,  is  at- 
tached directly  to  the  muscle-cell,  the  effector. 
As  a  matter  of  fact,  a  number  or  a  group  of  re- 
ceiving cells  are  attached  to  a  number  or  a 
group  of  muscle-cells.  Further,  this  arrange- 
ment "is  complicated  by  the  fact  that  the  cen- 
tral branches  of  the  receptive  cells  are  not  only 
applied  to  the  muscle-cells,  but  form  among 
themselves  a  network  of  communication  whereby 


26  THE  PHYSIOLOGY  OF  MIND 

the  impulses  that  arise  from  a  few  receptive 
cells  may  be  transmitted  to  many  muscle-cells 
instead  of  being  limited  to  a  restricted  group."1 
The  final  stage  consists  in  the  differentiation  of 
additional  cells  now  interposed  between  the 
primitive  receiving  cell  and  the  muscle-cells. 
The  network  now  becomes  exceedingly  com- 
plicated, but  it  presents  this  distinguishing 
feature,  its  fibers  are  continuous.  The  cells 
which  it  contains  are  clearly  primitive  nerve- 
cells  and,  as  already  stated,  Parker  has  applied 
to  them  the  term  "protoneurones."  Further, 
there  is  no  separation  of  these  protoneurones 
from  each  other  such  as  occurs  in  the  neurones 
of  vertebrates.  There  is  a  free  interchange  be- 
tween them  of  the  fibers  of  the  network.  There 
is  therefore  a  wide  diffusion  of  transmission 
which  is  totally  different  from  the  transmission 
along  definite  paths  as  seen  in  vertebrates.  It 
is  interesting  to  note,  however,  in  this  connec- 
tion that  even  in  vertebrates  nerve  nets,  diffuse 
and  continuous,  are  found  in  certain  struc- 
tures, namely,  in  the  walls  of  the  intestine  and 
in  the  heart  and  blood-vessels.  The  nerve  cells 
found  in  these  structures  present  all  the  char- 

1  See  Parker,  loc.  cit,  pp.  200,  201. 


THE   PHYSIOLOGY  OF  MIND  27 

acteristics    of    protoneurones,    and    as    in    the 
ccelenterates  form  a  continuous  network.1 

It  is,  however,  with  the  differentiated  neurone 
of  the  central  nervous  system  of  vertebrates 
that  we  are  most  concerned.  Here  the  cells 
which  give  rise  to  nerve-cells  are  in  the  embryo 
entirely  distinct  and  separate,  and  it  is  only  by 
developing  extensions  or  processes  that  one 
nerve-cell  comes  into  relation  with  other  nerve- 
cells;  but  there  is  never  any  fusion  or  exchange 
of  fibers  between  them.  Each  nerve-cell  is  a 
separate  and  distinct  histological  integer.  It  is 
a  unit  which  is  made  up  of  the  cell  body  and  the 
cell  processes.  By  means  of  the  latter  it  comes 
into  proximity  with  other  nerve-cells  often  far 
distant.  The  processes  terminate  in  brush-like 
tufts,  basket-like  formations,  and  in  other  ways. 
The  approximated  end-formations  of  two  nerve- 
cells  is  spoken  of  very  appropriately  as  a  syn- 
apse. The  nerve-cell,  in  general  terms,  is  made 
up  of  a  cell  body  and  two  kinds  of  processes;  at 
one  extremity  are  found  one  or  multiple  proc- 
esses leading  to  the  cell  body;  these  are  known 
as  the  dendrites;  at  the  other  extremity  is  found 
a  process  leading  from  the  cell   body;   this  is 

1  See  Parker,  loc.  cit.,  pp.  118,  128. 


28  THE  PHYSIOLOGY  OF  MIND 

known  as  the  axone.  To  this  entire  structure 
Waldeyer  in  1891  applied  the  term  "neurone,'' 
which  has  been  universally  accepted  and  is  now 
in  common  use.  Occasionally  there  is  more  than 
one  axone;  quite  frequently,  too,  the  axone 
gives  off  small  side  branches,  usually  near  the 
cell  body;  these  are  known  as  collaterals. 

For  a  discussion  of  nervous  function  clear 
conceptions  of  nervous  structure  are  absolutely 
essential.  To  repeat,  then,  the  neurone  cor- 
responds morphologically  to  one  cell;  it  is  an 
anatomical  and  genetic  unit.  It  comes  into 
close  relations  with  other  neurones,  but  remains 
anatomically  distinct  and  separate.  The  point 
or,  rather,  the  structure  at  which  the  juxta- 
position of  the  processes  of  two  neurones  takes 
place — the  synapse — assumes,  therefore,  a  spe- 
cial importance  in  the  problem  of  transmission.1 
Not  only  the  independence  of  the  individual 
neurone  but  the  presence  of  the  synapse  dis- 
tinguishes the  nervous  system  of  the  higher 
animals  from  that  of  the  ccelenterates,  and  it 

1  Instead  of  the  cells  coming  into  relation  by  the  approximation  of 
the  end-tufts  of  the  axone  of  one  cell  to  the  dendrites  of  another,  the 
end-tufts  of  the  axone  of  one  cell  may  terminate  about  the  body  of  the 
second  cell,  but  in  neither  case  is  there  any  fusion  or  continuity  of  struc- 
ture. 


THE   PHYSIOLOGY  OF  MIND  29 

may,  therefore,  be  spoken  of  as  a  synaptic  ner- 
vous system  in  contrast  with  the  nerve-net  of 
the  ccelenterates  which  is  essentially  syncytic. 

A  very  important  fact  now  becomes  mani- 
fest. In  the  nerve  net  of  the  ccelenterates  trans- 
mission is  essentially  diffuse  in  character.  Only 
in  a  very  limited  degree  is  the  response  to  a 
stimulus  differentiated.  According  to  Parker,  a 
stimulus — e.  g.,  a  fine  glass  rod — applied  to  a 
single  spot  on  the  body  of  a  sea-anemone  may 
be  followed  by  a  contraction  of  its  whole  mus- 
culature.1 However,  if  the  stimulus  be  less 
vigorous  and  limited — e.  g.,  if  light  be  thrown 
on  one  side  of  the  animal — it  responds  usually 
by  turning  its  oral  disc  toward  the  light.  Again, 
stimulation  of  its  tentacles  by  food  will  cause  its 
transverse  mesenteric  muscles  to  contract  and 
thus  open  its  oesophagus.  Further,  transmis- 
sion though  diffuse  in  certain  nerve-nets  takes 
place  more  readily  in  one  direction  than  in 
another;  e.  g.,  in  the  tentacles  of  the  sea- 
anemone,  in  which  transmission  is  much  more 
freely  accomplished  in  a  proximal  direction  than 
in  a  distal  one.  This  slight  tendency  to  spe- 
cialization in  the  responses  exhibited   by   the 

1  Loc.  cit.,  pp.  99,  100,  307. 


30  THE  PHYSIOLOGY  OF  MIND 

sea-anemone  is  to  be  looked  upon  as  the  fore- 
runner of  the  extremely  specialized  and  limited 
responses  met  with  in  the  higher  animals.  How- 
ever, while  a  nerve-net  may  transmit  more 
freely  in  one  direction  than  another,  it  really 
transmits  in  all.  Transmission  in  one  direc- 
tion, that  is,  polarity  of  transmission,  exists  in 
a  very  imperfect  degree  in  the  nerve-net.  In 
the  synaptic  nervous  system,  however,  it  is  not 
only  established,  but  is  absolute.  For  example, 
while  it  is  possible  to  elicit  a  response  to  a 
stimulus  applied  in  the  course  of  an  afferent 
neurone  of  the  spinal  cord,  as  in  obtaining  a 
spinal  reflex,  no  amount  of  stimulus  applied  to 
the  efferent  neurone,  for  instance,  to  the  cen- 
tral end  of  a  divided  motor  spinal  root,  will 
elicit  any  response  whatever.  Were  it  not  for 
the  synapses  and  the  consequent  polarity  of 
the  neurone,  a  stimulus  so  applied  should  dif- 
fuse to  other  neurones  in  the  cord;  e.  g.,  to  sen- 
sory neurones  and  from  these  again  to  motor 
neurones,  and  thus  lead  to  a  response;  but  none 
takes  place. 

It  is  to  the  synaptic  nervous  system  of  the 
vertebrates  that  we  will  now  direct  our  atten- 
tion.    We  have  already  seen  that  the  smooth 


THE   PHYSIOLOGY  OF  MIND  31 

muscle-cell  of  the  pore-canal  of  the  sponge  re- 
sponds to  a  direct  stimulation.  In  the  coelen- 
terates  a  receiving  cell  is  interposed  between 
the  muscle  and  the  stimulus.  The  muscle  mani- 
fests the  response;  it  is  the  effector;  the  receiv- 
ing cell  is  the  receptor.  At  the  next  stage  of 
differentiation,  as  already  pointed  out,  another 
cell  is  interposed  which  now  transmits  the  im- 
pulse from  the  receptor  to  the  effector.  In  ver- 
tebrates this  constitutes  the  simplest  expression 
of  a  response,  or,  to  use  the  physiological  term, 
a  reflex.  An  impression  is  made  on  the  cuta- 
neous surface,  is  transmitted  along  the  dendrite 
of  the  afferent  neurone;  thence  to  the  cell  body 
of  the  latter;  thence  along  its  axone  to  its  end- 
tufts  which  are  in  relation  with  the  dendrites 
of  the  transmitting  cell  and  form  with  the 
latter  a  synapse;  thence  to  the  body  of  the 
transmitting  cell  (the  motor  cell  in  the  ventral 
horn  of  the  cord),  and  thence  by  the  axone  of 
this  transmitting  cell  to  the  end-plate  on  the 
muscle-fiber.  The  mechanism  of  the  response 
does  not,  however,  remain  as  simple  as  this;  for 
other  neurones,  intercalary  neurones,  are  fur- 
ther interposed;  thus  a  neurone  may  be  inter- 
posed between  the  afferent  cell  or  receptor,  the 


32  THE  PHYSIOLOGY  OF  MIND 

sensory  neurone,  and  the  motor  neurones.  The 
effect  of  such  an  intercalary  neurone  ma}'  be 
twofold:  first,  it  may  reinforce,  i.  e.,  increase 
the  volume  and"  intensity  of  the  transmission: 
secondly,  it  may  come  into  relation  with  neu- 
rones other  than  the  ones  between  which  it  is 
interposed  and  thus  make  possible  a  more  ex- 
tensive and  a  more  complicated  response.  An 
a  'priori  consideration  would  suggest  that  there 
are  necessarily  great  variations  in  the  sim- 
plicity or  complexity  of  the  responses  as  well  as 
wide  variations  in  the  degree  with  which  such 
responses  are  fixed  or  stereotyped.  These  in- 
ferences, I  need  hardly  add,  are  in  accord  with 
fact.  In  the  spinal  reflexes,  for  instance,  we  have 
examples  of  relative  simplicity  and  stereotypy 
of  response.  In  the  knee-jerk  we  have  an  ex- 
ample of  an  exceedingly  simple  and  fixed  re- 
sponse. It  is  invariably  the  same  and  inde- 
pendent of  volition;  it  is  subject,  of  course,  to 
variations  in  diffusion  and  degree  dependent 
upon  secondary  factors,  but  its  character  never 
changes.  The  neural  mechanism  upon  which  it 
depends  is  relatively  simple. 

However,  the  very  simplicity  and  stereotypy 
of  the  knee  reflex  bespeaks  a  response  that  has 


THE  PHYSIOLOGY  OF  MIND  33 

become  differentiated  and  limited,  and  it  serves 
our  present  purpose  merely  as  offering  an  ex- 
ample of  a  simple  mechanism  of  spinal  re- 
sponse. It  is  exceedingly  probable  that  in  the 
course  of  development  differentiations  of  lim- 
ited relationships  between  intercalary  neurones 
and  efferent  neurones  ensued  relatively  late,  and 
that  the  primitive  arrangement  was  one  which 
permitted  of  the  more  or  less  wide  diffusion  of 
the  stimuli  received  by  the  afferent  neurones. 
In  keeping  with  this  we  note  in  the  fish  in  re- 
sponse to  such  stimuli  movements  which  in- 
volve the  musculature  of  the  entire  trunk.  Evi- 
dently the  mechanism  of  response  must  at  first 
have  been  very  general  in  character.  It  must 
have  consisted  in  the  linking  of  intercalary  neu- 
rones and "  the  consequent  formation  of  path- 
ways of  transmission  general  in  character,  and, 
furthermore,  common  to  the  transmission  of 
stimuli  received  from  many  different  receptors. 


Having  laid  a  foundation  for  the  conception 
of  the  mechanism  by  means  of  which  stimuli  are 
received  and  transmitted,  let  us  now  turn  our 
attention  briefly  to  the  stimuli  which  the  or- 


34  THE   PHYSIOLOGY  OF  MIND 

ganism  is  capable  of  receiving.  Thus  far  we 
have  considered  merely  the  most  primitive  of 
all  stimuli,  namely,  contact  with  foreign  bodies. 
Such  contact  constitutes  an  impact  grossly 
mechanical  or  physical  in  character.  Evidently, 
living  protoplasm  is,  in  addition,  exposed  to 
actions  that  are  chemical,  to  the  movements  and 
course  vibrations  of  the  medium  in  which  it  is 
immersed,  as  well  as  to  the  various  forces  that 
pervade  the  physical  world. 

Protoplasm  is,  of  course,  destroyed  by  any 
chemical  action  that  radically  interferes  with 
its  structure.  Living  protoplasm,  as  pointed 
out,  is  an  exceedingly  complex  colloid;  it  is 
relatively  unstable  and  is  constantly  undergoing 
change.  It  is  being  constantly  built  up  and  yet 
is  being  constantly  oxidized  and  reduced.  Such 
changes  necessarily  mean  an  interplay  within 
comparatively  narrow  limits.  If  living  proto- 
plasm is  exposed,  for  instance,  to  the  gross  ac- 
tion of  an  acid  or  an  alkali,  its  destruction 
necessarily  follows.  There  is,  however,  a  wide 
range  in  which  chemical  action  can  take  place 
without  such  result.  Such  non-destructive  ac- 
tion would  naturally  be  influenced,  first,  by  the 
nature  of  the  substance   diffused  through  the 


THE   PHYSIOLOGY  OF  MIND  35 

surrounding  medium,  and  secondly,  by  the  de- 
gree of  its  dilution.  The  reaction  of  the  proto- 
plasm to  such  influences  cannot,  of  course,  be 
observed  by  us  through  the  microscope,  but 
that  such  chemical  actions  do  take  place  is 
evidenced  to  us  in  our  own  persons  by  our 
senses  of  taste  and  smell.  Further,  it  will  be- 
come apparent  as  we  proceed  that  the  reaction 
of  the  organism  to  the  chemical  impressions  of 
the  environment  have  profoundly  influenced  the 
development  of  the  nervous  system. 

When  we  turn  our  attention  to  the  move- 
ments and  vibrations  of  the  medium  in  which 
the  protoplasm  is  immersed,  we  at  once  find 
numerous  evidences  that  the  protoplasm  reacts 
to  such  influences.  In  the  very  simplest  forms, 
such  as  the  protozoa,  the  coarse  movements  of 
the  water — currents  and  the  like — possibly  facili- 
tate the  changes  implied  by  oxidation,  but  do 
nothing  else.  Soon,  however,  in  the  metazoa 
we  observe  the  appearance  of  small  cavities — 
vesicles — which  contain  one  or  more  particles 
of  solid  mineral  matter  and  which  constitute  an 
apparatus  by  means  of  which  the  movements, 
the  vibrations,  of  the  surrounding  medium  are 
taken  up — arrested  as  it  were — and  thus  for- 


36  THE  PHYSIOLOGY  OF  MIND 

cibly  transmitted  to  the  body  of  the  organism. 
Such  an  apparatus,  though  it  is  termed  an  ear, 
an  otic  vesicle,  may  take  up  movements  far 
coarser  than  those  which  in  ourselves  give  rise 
to  sound.  Again,  in  fishes  there  is,  in  addition 
to  a  well-differentiated  ear,  an  apparatus  which 
extends  in  linear  form  from  the  head  on  each 
side  of  the  body  to  the  tail.  It  is  known  as  the 
lateral  line  system  and  consists  of  a  tube  having 
at  intervals  an  open  space  closed  by  a  mem- 
brane beneath  which  is  found  a  structure  in- 
distinguishable in  its  essential  features  from  a 
macula  acustica.  Each  such  macula  contains 
epithelial  cells  bearing  hair-like  appendages  and 
each  is  surmounted  by  a  small  jelly-like  mass 
containing  a  few  granules  of  mineral  matter. 
It  is  exceedingly  probable  that  this  apparatus, 
existing  as  it  does  in  addition  to  the  ear,  has  to 
do  with  the  reception  of  vibrations  other  than 
those  of  sound;  namely,  waves  and  movements 
of  relatively  great  length.1 

It  would  appear,  then,  that  in  addition  to  the 
chemical  impressions  of  the  environment,  the 
movements  and  vibrations  of  the  surrounding 

1  See,  among  others,  Dercum,  Proceedings  Academy  of  Nat.  Sci., 
Philadelphia,  1879,  p.  152. 


THE  PHYSIOLOGY  OF  MIND  37 

medium  are  taken  up  in  greater  or  less  degree 
by  living  protoplasm.  These  movements  seem 
to  play  an  indifferent  role  in  the  protozoa  and 
in  plant  life,  but  in  metazoa  an  apparatus  sooner 
or  later  makes  its  appearance,  the  function  of 
which  is  to  arrest  and  to  transmit,  and,  in  many 
instances,  to  magnify  what  is  purely  a  mechan- 
ical or  physical  impression. 

Similarly,  living  protoplasm  has  the  function 
of  taking  up  other  incident  forces.  Especially  is 
this  the  case  in  regard  to  light.  The  simpler 
forms  of  life — -e.  g.,  the  amoeba  and  other 
protozoa — are  largely  transparent  to  light.  It 
is  probable  that  the  light  vibrations  so  trans- 
mitted influence  notwithstanding  the  chemical 
changes  in  the  protoplasm;  indeed,  this  is  so 
evident  in  plant  life  as  to  admit  of  no  question. 
However,  very  early  we  note  in  many  protozoa 
the  appearance  of  a  small  mass  of  red  or  dark 
red  pigment,  a  so-called  eye  spot  or  stigma,  a 
mass  which  clearly  is  not,  or  is  less,  transparent 
to  light  than  the  remaining  protoplasm,  and 
whose  action  is  apparently  to  arrest  and  trans- 
form the  light  vibrations  and,  possibly,  to  trans- 
mit this  transformed  energy  to  the  general  pro- 
toplasmic mass.     Clearly  we  have  here  a  mech- 


38  THE  PHYSIOLOGY  OF  MIND 

anism,  a  modification  of  structure,  analogous 
to  the  formation  of  the  otic  vesicle,  the  function 
of  which  with  its  contained  mineral  granules 
(otoliths)  is  obviously  to  arrest  and  transmit 
coarse  physical  vibrations. 

Heat  likewise  greatly  influences  the  activity 
of  living  protoplasm.  The  reactions  of  amoebae 
and  other  protozoa  to  variations  in  tempera- 
ture are  well  known.  Whether  in  given  forms 
the  eye  spots,  the  stigmata,  play  here  also  a 
role  is  not  known,  though  it  is,  of  course,  not 
improbable.  However,  the  presence  of  the 
stigmata  is  clearly  not  necessary  to  the  tem- 
perature reactions  of  the  primitive  organism. 
All  things  considered,  special  structures  for  the 
"taking  up"  of  heat  rays  do  not  appear  to  be 
developed  until  late  in  the  evolution  of  the 
metazoa,  and  our  knowledge  of  them  is  largely 
inferential.  Regarding  their  actual  existence, 
however,  there  can  be  no  doubt;  of  this  our 
ability  to  appreciate  hot  and  cold  and,  indeed, 
many  gradations  of  temperature,  offers  indis- 
putable evidence. 

A  very  striking  fact  now  becomes  apparent, 
namely,  that  the  various  mechanisms  for  the 
special  reception  of  the  incident  forces  of  the 


THE  PHYSIOLOGY  OF  MIND  39 

environment  are  exceedingly  small  in  number. 
They  are  limited  to  receptors  for  contact,  for 
coarse  movements  and  vibrations  of  the  sur- 
rounding medium,  for  chemical  changes,  and  for 
the  forces  of  light  and  heat.  This  is  essentially 
the  arrangement  in  the  higher  metazoa  and 
notably  in  our  own  persons.  This,  however, 
leaves  the  organism  without  any  provision  for 
the  reception — appreciation — of  vast  ranges  of 
vibrations  of  whose  existence  we  have  in  con- 
sequence only  an  inferential  knowledge.  Be- 
sides contact,  touch  will  give  us  information 
only  of  coarse  vibrations  numbering  less  than 
30  per  second;  thence,  vibrations  from  30  to 
30,000  per  second  are  appreciated  by  the  ear. 
Now  ensues  a  great  hiatus,  for  the  organism  is 
unable  to  appreciate  any  vibrations  between 
30,000  per  second  and  3000  billion  per  second. 
Vibrations  from  3000  billion  to  800,000  billion 
are  appreciated  as  radiant  heat;  400,000  billion 
to  800,000  billion  are  appreciated  as  light.  For 
vibrations  from  800,000  billion  to  6,000,000,000 
billion,  embracing  the  ultra-violet  rays  and  the 
z-rays,  there  is  no  appreciation  whatever.1 

1  Herrick,  Introduction  to  Neurology,  second  edition,  p.  77. 


40  THE   PHYSIOLOGY  OF  MIND 

When  we  consider  the  vast  range  and  number 
of  the  forces  at  work  in  the  universe,  the  ex- 
ceedingly limited  capacity  of  the  organism  to 
become  cognizant  of  its  environment  becomes 
very  apparent.  Living  protoplasm  fails  utterly 
to  develop  receptors  for  these  unnumbered 
manifestations  of  energy.  Protoplasm  seems  to 
be  "transparent"  to  them.  Have  we  not  a 
hint  here  as  to  the  structure  of  protoplasm?  If 
deluged  by  them  in  great  volume  it  may  be  de- 
stroyed, but  as  ordinarily  exposed  in  the  course 
of  nature  to  electricity,  the  ultra-violet  ray,  the 
#-ray,  and  other  rays  it  remains  unaffected.  It 
is  very  suggestive,  too,  that  it  is  practically 
transparent  to  light  rays  and  is  obliged  to  de- 
velop a  pigment,  the  stigma,  the  visual  purple. 
Similarly,  it  is  largely  negative  to  coarse  vibra- 
tions and  requires  the  development  of  a  vesicle 
with  its  contained  otolith. 

In  order  that  the  significance  of  the  above 
facts  may  be  fully  appreciated .  let  us  recall  to 
our  minds  once  more  the  nature  of  living  proto- 
plasm. It  is,  as  we  have  already  pointed  out, 
an  exceedingly  complex  colloid,  built  up  of  many 
complex  amino-acids  distributed  through  varied 
disperse  and  continuous  phases.     It  is  a  very 


THE   PHYSIOLOGY  OF  MIND  41 

unstable  compound,  for  it  is  constantly  under- 
going changes.  It  is  constantly  being  oxidized 
and  reduced,  but  is  as  constantly  being  built 
up.  Foreign  materials,  proteins,  fats,  and  car- 
bohydrates are  through  its  fermentative  (t.  e., 
chemical,  electro-physical)  action  fragmented 
until  they  become  identical  in  character  with 
the  molecules  of  the  original  protoplasmic  mass 
and  become  part  of  its  substance.  During  this 
process  and  in  the  further  continuance  of  the 
chemical  change,  that  is,  in  the  continued  proc- 
ess of  oxidation,  energy  is  liberated.  The  older 
particles  are  finally  chemically  so  far  reduced 
that  they  become  inert  and  then  spontaneously 
make  their  exit  by  solution  into  the  surrounding 
medium.  It  is  this  continuous  chemical  change 
with  its  accompanying  evolution  of  energy  that 
constitutes  the  phenomenon  presented  by  living 
matter.1 

Evidently,  if  so  complex  and  unstable  a  com- 
pound as  living  protoplasm  when  first  evolved 
had  been  vulnerable  to  the  innumerable  in- 
cident forces  of  the  universe,  it  could  never 
have  survived.     Curiously,  it  has  been  almost 

1  The  mineral  salts — ions  of  the  crystalloids — undoubtedly  arrange 
themselves  during  this  process  in  accordance  with  electrophysica' 
principles,  and  no  doubt  play  an  important  rdle. 


42  THE  PHYSIOLOGY  OF  MIND 

wholly  negative  in  its  reaction  to  these.  Ex- 
tremes of  heat  and  cold,  coarse  physical  de- 
struction, have  been  the  most  it  had  ordinarily 
to  contend  with.  Excessively  rarely  have  other 
agencies  interfered  with  its  existence.  Its  very 
"transparency"  has  been  its  salvation.  Perhaps 
it  is  its  complexity,  its  semifluidity — its  very  in- 
ability to  take  up  manifold  modes  of  motion — 
its  colloidal  plasticity,  its  peculiar  molecular 
structure,  that  have  made  possible  the  passage 
through  it  of  such  a  vast  array  of  forces  with- 
out change  in  its  substance.  After  all,  these 
forces  do  influence  it  and  play  a  role  in  its 
physics  and  chemistry,  but  certainly  that  role, 
as  it  occurs  in  nature — not  in  the  laboratory — 
is  not  a  destructive  one. 

We  have  already  considered  (see  p.  23)  the 
evolution  or  adaptation  in  metazoa  of  a  sur- 
face cell  to  receive  external  impressions,  e.  g., 
of  contact,  and  which  receiving  cell  (receptor) 
transmits  the  impact  or  impulse  to  a  contig- 
uous contractile  cell  (muscle-cell,  effector)  either 
directly  or  it  may  be  through  an  intermediate 
cell  or  cells.  Evidently  these  primitive  surface 
cells  were  capable  of  receiving  all  of  the  im- 
pressions which  the  protoplasm  itself  was  cap- 


THE   PHYSIOLOGY   OF  MIND  43 

able  of  receiving.  These  impressions  consisted 
primarily  of  those  of  contact  and  of  coarse 
vibration.  That  substances  contained  in  the 
medium  in  which  the  organism  was  immersed 
also  affected  the  surface  cells  chemically  is 
extremely  probable.  It  seems  equally  clear 
that  the  surface  cells  were  also  affected  by 
the  vibrations  which  give  rise  to  sound  and 
by  those  which  give  rise  to  heat  and  light.  In 
both  of  the  latter  instances,  however,  it  is  evident 
that  the  degree  and  extent  in  which  the  impacts 
could  be  taken  up  depended  upon  the  presence 
of  special  and  probably,  at  first,  purely  incidental 
factors;  on  the  one  hand,  on  the  presence  of 
coarse  mineral  particles,  and  on  the  other  of 
particles  of  pigment;  i.  e.,  of  particles  derived 
from  the  original  protoplasm  and  so  changed  as 
to  be  able  to  arrest  in  a  measure  the  incident 
forces. 

In  addition,  then,  let  us  repeat,  to  contact 
and  coarse  vibrations,  the  primitive  surface  re- 
ceiving cell  also  received  those  impacts  termed 
"chemical."  These  impacts,  molecular  in  char- 
acter, are  those  which,  as  already  pointed  out, 
give  rise  in  ourselves  to  the  sensations  of  smell 
and  taste.    It  would  seem  that  the  reception  of 


44  THE  PHYSIOLOGY  OF  MIND 

chemical  impressions  was  almost  as  primitive  if 
not  quite  as  primitive  a  quality  as  the  reception 
of  contact  and  coarse  vibrations.  On  a  priori 
grounds  we  would  almost  expect  the  chemical 
sense  or  senses  to  have  assumed  a  relatively 
high  degree  of  importance;  and  this,  indeed,  is 
found  to  be  the  case,  judging  from  the  facts  of 
vertebrate  morphology.  It  would  appear  that 
relatively  early  certain  receiving  cells  became 
especially  adapted  to  receiving  chemical  im- 
pressions and  that  this  finally  became  their 
special  and  sole  function.  It  is  important  at 
this  point  to  note  a  distinction  between  the 
senses  of  smell  and  taste.  The  sense  of  smell  is 
excited  by  objects  external  to  the  organism, 
usually  by  objects  at  some  distance,  and  the 
impressions  received  from  which  cause  the  or- 
ganism to  approach  or  to  move  away  from  the 
object.  The  sense  of  taste,  on  the  other  hand, 
deals  with  objects  that  have  entered  the  oral 
cavity  or  at  least  come  into  close  contact  with 
it  and  which  bring  about  responses  within  the 
body  of  the  animal,  namely,  visceral  responses 
dealing  with  digestion.  As  expressed  by  Sher- 
rington, the  sense  of  smell  is  exteroceptive,  while 
taste  is  interoceptive.     Clearly,  it  is  the  extero- 


THE   PHYSIOLOGY  OF  MIND  45 

ceptive  sense  of  smell  which  deals  directly  with 
the  environment  and  as  such  it  greatly  out- 
ranks in  importance  the  sense  of  taste.  In 
keeping  with  this  we  find  in  fishes  that  almost 
the  whole  of  the  cerebral  hemisphere  is  an 
organ  of  smell,  while  the  portion  devoted  to  the 
sense  of  taste  is  much  smaller  and  appears  to 
be  in  close  anatomical  relation  with  the  portion 
— the  visceral  area1 — devoted  to  impressions  re- 
ceived from  the  viscera.  However,  in  fishes  the 
receptors  for  taste  are  found  also  outside  of  the 
oral  cavity  about  the  mouth  and,  indeed,  in 
some  forms  are  rather  extensively  distributed 
externally;  so  that  in  fishes  the  sense  of  taste  is 
not  as  strictly  interoceptive  as  with  ourselves, 
but  also  in  part  exteroceptive.  The  great  im- 
portance of  smell  as  an  exteroceptive  sense  be- 
comes evident  when  we  reflect  upon  the  very 
great  range  in  the  number  and  variety  of  the 
impressions,  the  infinitely  small  size  of  the  par- 
ticles concerned,  and  the  relatively  great  dis- 
tance at  which  they  may  be  appreciated. 
Taste,  on  the  other  hand,  has  to  do  only  with 
substances  in  immediate  contact  with  the  re- 
ceptors, while  the  variety  of  impressions  pos- 

1  See  Herriek,  loc.  cit.,  pp.  119,  273. 


46  THE   PHYSIOLOGY  OF  MIND 

sible  is  exceedingly  small;  namely,  merely  salty, 
sour,  bitter,  and  sweet.  Flavors,  it  should  be 
remembered,  are  appreciated  only  through  the 
sense  of  smell. 

Just  as  in  the  course  of  development  special 
receptors  were  differentiated  for  chemical  im- 
pressions, special  receptors  were  differentiated 
for  the  reception  of  sound  and  light,  and  to  which 
have  been  adapted  various  structures  for  in- 
tensifying and  elaborating  the  impressions  re- 
ceived. A  consideration  of  the  latter  factors 
would  take  us  too  far  afield  and,  further,  is  not 
necessary  for  our  purpose.  Suffice  it  to  say  that 
highly  specialized  receptors  with  highly  complex 
additions  have  in  the  course  of  time  made  their 
appearance,  and  that  they  are  all  expressive  of 
a  common  truth,  namely,  that  they  receive  and 
transmit  into  the  interior  of  the  organism  cer- 
tain definite  impacts  from  the  external  world. 
That  there  are  more  than  five  pathways  for  the 
ingress  of  these  impacts  need  not  here  be 
pointed  out;  the  consideration  of  others  than 
those  thus  far  discussed  may  be  safely  deferred 
for  the  present. 

Having  emphasized  the  purely  physical  char- 
acter of  the  role  played  by  the  receptors,  let  us 


THE  PHYSIOLOGY  OF  MIND  47 

turn  our  attention  once  more  to  the  transmis- 
sion of  the  impacts  through  the  organism.  How 
does  the  organism  respond  to  the  multitude  of 
impressions  received?  What  are  the  reasons 
therefore?  In  how  far  are  responses  fixed?  In 
how  far  are  they  variable? 

The  simplest  form  of  response,  as  we  have 
already  seen,  is  the  response  of  a  muscle-cell  to 
direct  stimulation;  the  next  in  the  course  of 
evolution  is  the  reception  by  an  epithelial  cell, 
a  receptor,  of  the  impact,  and  the  transmission 
of  the  latter  to  a  contiguous  muscle-cell,  an 
effector;  the  third  state  consists  in  the  inter- 
polation between  the  receptor  and  the  effector 
of  another  cell  whose  function  is  that  purely  of 
transmitting  the  impact  from  the  first  cell  to 
the  second.  This  third  cell  may  have  relations, 
however,  with  several  effectors,  and  thus  the 
response  induced  may  be  less  simple  and  pro- 
portionately extended.  This  intermediate  cell 
has  been  termed  by  biologists  the  "adjustor." 
It  should,  of  course,  have  a  definite  name,  but 
to  the  writer  it  has  seemed  that  the  word  "ad- 
justor," implying  as  it  does  independence  of 
action  or  possibly  volition,  is  open  to  objection. 
The  action  of  the  intermediate  cell  is  purely 


48  THE  PHYSIOLOGY  OF  MIND 

physical  and,  needless  to  say,  automatic.  Its 
presence,  however,  opens  up,  as  we  will  see, 
enormous  possibilities  as  to  the  degree  and  the 
character  of  the  response.  As  already  pointed 
out  (see  p.  31),  other  transmitting  cells,  inter- 
calary neurones,  are  in  the  course  of  develop- 
ment farther  interposed.  The  role  of  the  latter 
in  increasing  the  volume  and  intensity  of  the 
transmission  and  in  adding  to  the  complexity  of 
the  response  we  have  already  indicated. 

Evidently  the  presence  of  the  intercalary 
neurones  has  made  possible  the  establishment 
of  definite  pathways  of  transmission.  Impacts 
derived  from  many  sources  would  tend  to  form 
average  pathways  of  transmission  to  the  ef- 
fectors. To  use  the  words  of  Sherrington,  "That 
portion  of  the  synaptic  nervous  system  which 
is  termed  'central'  is  the  portion  where  the 
nervous  paths  from  various  peripheral  organs 
meet  and  establish  paths  in  common,  i.  e., 
'common  'paths* '  The  central  nervous  system 
of  vertebrates  is  primitively  a  longitudinal 
tubular  structure  which  lies  above  another 
longitudinal  tubular  structure  upon  which  the 
nutrition  of  the  animal  depends,  namely,  the 
alimentary  canal.     The  material  admitted  to 


THE  PHYSIOLOGY  OF  MIND  49 

the  latter  traverses  its  entire  length.  Evidently 
the  reception  of  material  which  may  serve  as 
food  is  of  primal  importance  to  the  animal. 
Given  the  "polarity"  of  the  latter — i.  e.,  the 
differentiation  of  a  cephalic  and  a  caudal  ex- 
tremity— it  follows  that  the  interplay  of  re- 
ceptors and  effectors  to  bring  about  the  intake 
of  food  at  the  cephalic  end  is  a  necessary  out- 
come of  the  action  of  the  individual  receptors 
and  the  establishment  of  common  paths  of 
transmission.  The  primitive  nervous  system  of 
vertebrates  was  in  its  essentials  a  tube  in  which 
the  nerves  coming  from  the  peripheral  surfaces 
terminated  synaptically  in  neurones  in  the  walls 
of  the  tube;  probably  there  was  an  arrangement 
in  segments,  certain  nerve  aggregations  corre- 
sponding to  certain  areas.  These  tubal  centers 
were  doubtless  connected  with  each  other  by 
intercalary  neurones  which  communicated  syn- 
aptically with  each  other  to  form  "internuncial 
paths."  In  this  way  many  muscles  would  prob- 
ably be  made  to  respond  simultaneously  or  suc- 
cessively to  an  impression  made  upon  a  limited 
number  of  cutaneous  receptors.  If  we  turn  our 
attention  to  the  cephalic  end  of  the  animal,  we 
note   the   presence   of   certain   aggregations   of 


50  THE  PHYSIOLOGY  OF  MIND 

neurones  about  the  tube  which  stand  in  definite 
relation  to  certain  receptors  situated  about  the 
head,  the  relation  being  very  much  the  same  as 
the  segmental  relation  in  the  tube  lower  down. 
Here,  to  restate  .the  fact,  definite  cutaneous 
levels  of  receptors  are  related  to  the  neurone 
aggregations  at  the  same  levels,  each  such  ar- 
rangement constituting  a  segment. 

The  first  aggregation  of  neurones  that  we 
meet  with  in  the  primitive  vertebrate  forms  is 
that  constituting  the  olfactory  lobe  which  is  in 
close  relation  with  the  receptors  in  the  olfactory 
mucous  membrane.  Back  of  the  olfactory  lobe 
we  note  the  presence  of  a  lobe  related  to  the 
receptors  in  the  eye;  next  an  aggregation  re- 
lated to  the  receptors  in  the  ear,  and  so  on. 
Naturally  these  facts  find  their  simplest  ex- 
pression in  the  fish.  Speaking  of  the  dog-fish, 
Herrick  states1  that  we  may  recognize  in  this 
fish  a  "nose  brain,"  an  "eye  brain,"  an  "ear 
brain,"  a  "visceral  brain,"  and  a  "skin  brain." 
Each  "brain"  is  related,  let  us  repeat,  to  certain 
receptors  and  to  these  only.  Further,  each  set 
of  receptors  and  its  corresponding  central  neu- 
rones is  adapted  to  the  reception  of  certain  im- 

1  See  Herrick,  loc.  cit.,  p"  121. 


THE  PHYSIOLOGY  OF  MIND  51 

pacts  or  stimuli  only;  thus  the  receptors  for  the 
olfactory  lobes  can  receive  only  chemical  im- 
pressions; the  receptors  for  the  optic  lobes  only 
the  impacts  of  light;  those  for  the  ear  only  the 
impacts  of  sound,  and  so  on.  In  other  words, 
each  receptor  can  accept  only  its  own  special 
stimulus;  the  latter  is  known  technically  as  the 
"adequate"  stimulus. 

We  are  impressed  at  once  by  the  relatively 
enormous  size  in  the  fish  of  the  olfactory  lobes. 
We  are  justified  in  inferring  that  the  chemical 
sense  in  fishes  is  most  important.  Its  receptors 
are  placed  immediately  above  the  oral  cavity 
and  its  function  in  the  approach  of  the  organ- 
ism to  food  and  in  the  intake  of  food  is  quite 
obvious.  We  note  that  the  chemical  impacts, 
i.  0.,  odors,  are  often  received  from  great  dis- 
tances. The  question  arises  why  does  the 
organism  as  a  whole  respond  to  the  reception  of 
such  impacts  by  an  approach?  Here  we  are 
forced  in  a  measure  into  the  field  of  speculation. 
However,  the  phenomenon  must  be  purely 
physical  and  therefore  capable  of  a  physical 
interpretation.  Once  more  we  are  referred  to 
the  reactions  of  living  protoplasm  to  the  impacts 
of  the  external  world.    Evidently  these  impacts 


52  THE  PHYSIOLOGY  OF  MIND 

can  be  roughly  divided  into  two  groups:  first, 
those  whose  motions  can  be  taken  up  by  the 
protoplasm  with  little  or  no  consumption  of  its 
own  substance,  and,  secondly,  those  in  which 
the  vibrations  or  molecular  movements  im- 
parted by  the  impacts  tend  to  disrupt,  to  dis- 
organize, or  destroy  its  structure.  Evidently, 
chemical  impressions  which  are  in  harmony  or 
in  consonance  with  the  protoplasm  of  the  ol- 
factory receptors,  or,  to  state  it  in  other  words, 
whose  chemical  or  physical  motions  are  ac- 
cepted and  transmitted  by  the  receptors  with 
no  or  a  minimal  change  in  the  protoplasm  of 
the  latter,  establish  a  direction  of  least  resist- 
ance. Possibly  this  reaction,  in  its  essence, 
does  not  differ  from  that  which  leads  the  amoeba 
to  throw  out  a  pseudopod  toward  a  neighbor- 
ing mass  of  food.  In  the  latter  (as  we  have 
already  seen  on  p.  13)  we  have  reason  to  believe 
that  the  phenomenon  is  purely  physical  or 
dynamic. 

Internuncial  fibers  connect  the  olfactory  lobes 
with  the  centers  lower  down,  namely,  with  the 
neurones  in  the  spinal  cord  which  innervate  the 
muscles  on  either  side  of  the  trunk.  In  response 
to  an  impression  received  primarily  through  the 


THE  PHYSIOLOGY  OF  MIND  53 

olfactory  receptors  these  muscles  contract.  The 
neurones  which  supply  the  two  sides  are  syn- 
aptically  so  related  that  when  the  muscles  of 
one  side  of  the  trunk  contract,  contraction  of 
the  muscles  of  the  other  side  is  inhibited.  The 
result  is  an  alternate  contraction  of  the  muscles 
of  the  two  sides,  which  causes  the  body  of  the 
animal  to  be  propelled  forward  as  in  swimming. 
The  neurone  relationships  which  necessitate  the 
alternate  contractions  and  alternate  inhibitions 
or  relaxations  of  the  two  sides  are  in  part  direct 
and  in  part  indirect  through  the  cerebellum. 
With  these  subsidiary  problems  we  are,  how- 
ever, not  at  present  concerned. 

Should  the  chemical  impressions  be  harmful 
or  of  such  a  nature  as  to  portend  harm,  it  is 
easy  to  understand  how  reverse  movements 
should  occur  and  the  animal  be  moved  away. 
Everything  depends  upon  the  development  of 
the  internuncial  paths.  The  latter  are  clearly 
association  paths  which  when  once  fully  de- 
veloped respond  accurately  and,  it  is  needless 
to  add,  automatically  to  the  olfactory  im- 
pressions. Further,  it  is  very  probable  that  in 
the  course  of  evolution  these  olfactory  impres- 
sions would  not  necessarily  be  limited  to  those 


54  THE  PHYSIOLOGY  OF  MIND 

which  merely  affected  the  protoplasm  of  the 
receptors  for  good  or  for  ill,  but  for  those  which 
affected  the  tissues  of  the  organism  as  a  whole. 
While  the  reader  may  find  objection  to  the  above 
explanation,  the  fact  remains,  I  think,  beyond 
reasonable  question  that  the  approach  or  re- 
treat of  the  fish  in  response  to  olfactory  im- 
pressions is  a  purely  automatic  phenomenon. 

When  we  turn  our  attention  to  the  eye,  the 
ear,  and  the  lateral  line  system  of  the  fish,  other 
important  and  interesting  facts  suggest  them- 
selves. Thus  it  is  exceedingly  probable  that  the 
field  of  vision  is  primarily  one  for  the  perception 
of  moving  objects  rather  than  for  those  which 
are  stationary.  Food,  already  perceived  by  its 
odor,  makes  also  in  moving  an  impression  on 
the  retina.  Owing  to  the  internuncial  path- 
ways the  action  of  the  olfactory  apparatus  in 
bringing  about  contraction  of  the  muscles  in 
swimming  would  now  be  reinforced.  A  similar 
effect  would  be  exerted  if  the  object  also  made  a 
sound  and  so  excited  the  ear,  or  produced  coarse 
waves  in  the  water  and  so  excited  the  lateral 
lines. 

Whatever  explanation  we  adopt,  whether  we 
consider   the   olfactory   impacts — the   chemical 


THE  PHYSIOLOGY  OF  MIND  55 

molecular  movements  of  smell — as  establishing 
a  line  of  least  resistance,  or  whether  we  adopt 
the  explanation  of  these  impacts  establishing  an 
"attraction,"  the  conclusion  is  alike  inevitable 
that  the  resulting  approach  of  the  fish  toward 
the  food  is,  let  us  repeat,  automatic.  Similarly 
the  reaction  of  the  other  "brains"  to  their  spe- 
cial receptors — the  eye  brain,  the  ear  brain,  the 
skin  brain — must  be  alike  physical  and  auto- 
matic. 

It  may,  I  think,  be  safely  assumed  that  the 
other  functions  of  the  fish  in  which  the  nervous 
system  plays  a  part,  such  as  digestion,  respira- 
tion, circulation,  and  nutrition,  are  similarly 
automatic;  in  fine,  that  all  the  neural  functions 
are  automatically  performed.  The  question 
arises  can  we  draw  a  like  conclusion  as  regards 
the  nervous  system  of  the  higher  vertebrate 
forms,  including  man?  Let  us  see  what  the 
facts  justify. 

The  automatic  character  of  a  spinal  response 
or  reflex  must  be  admitted  without  question. 
Secondly,  this  response  is  fixed  and  invariable. 
A  similar  interpretation  must,  I  think,  be  ex- 
tended to  the  responses  which  involve  the  brain 
stem,  namely,  the  medulla,  the  pons,  the  crura 


56  THE  PHYSIOLOGY  OF   MIND 

cerebri,  the  thalamus,  and  the  corpus  striatum; 
indeed,  the  brain  stem  is  frequently  spoken  of 
as  a  segmental  apparatus,  just  as  we  apply  the 
conception  of  a  segmental  apparatus  to  the 
spinal  cord.  It  is  also  spoken  of  as  the  palseo- 
encephalon  (Edinger)  as  it  represents  the  prim- 
itive vertebrate  brain.  To  the  brain  stem  we 
must  add  the  cerebellum  whose  activities  are 
alike  "invariable,  innate,  structurally  predeter- 
mined."1 This  leaves  us  as  the  only  structure 
permitting  a  variable  response  the  cerebral 
cortex. 

It  may  be  here  noted  that  such  modifications 
of  the  invariable  response  as  an  animal  betrays 
in  its  behavior  under  changed  external  condi- 
tions, such  as  absence  or  surplus  of  food  or  of 
oxygen,  or  such  changes  in  response  as  may  have 
their  origin  in  changed  physiological  states 
within  the  organism  itself,  are  not  here  included 
in  the  expression  "variable"  response,  but  rather 
such  responses  as  would  suggest,  other  things 
equal,  a  volitional  act,  i.  e.,  "choice"  on  the 
part  of  the  animal.  "Choice"  in  this  sense  is 
manifested  by  such  elementary  forms  as  the 
amoeba,  and,  as  we  have  seen,  by  the  individual 

1  See  Herrick,  loc.  cit.,  p.  124. 


THE  PHYSIOLOGY  OF  MIND  51 

cells  of  the  body  tissues.  How  this  apparent 
choice  is  to  be  explained  on  purely  physical  and 
chemical  principles  we  have  also  seen.  Let 
us  now  take  up  the  "variable"  responses  of  the 
higher  vertebrates  for  detailed  consideration. 

The  end  of  the  primitive  neural  tube,  the 
telencephalon,  also  spoken  of  as  the  neo-en- 
cephalon,  has  no  segmental  relationships.  It 
can,  therefore,  only  be  in  relation  with,  and 
grow  in  relation  with,  the  other  portions  of  the 
neural  tube.  Its  neurones  in  their  development 
and  multiplication  can  only  establish  relation- 
ships with  the  neurones  of  the  primitive  seg- 
mental brain;  ingress  and  egress  are  possible 
only  through  the  latter.  Not  having  segmental 
relationships,  the  neurones  of  the  end-brain  are 
necessarily  limited  to  the  function  of  intercalary 
neurones.  If  the  end-brain  grows  in  response 
to  the  stimulus  of  function — and  the  facts  of 
embryology,  comparative  anatomy,  and  pale- 
ontology show  that  it  has  so  grown — it  means 
that  a  multiplication  of  intercalary  neurones 
has  taken  place,  and  as  a  corrollary  an  increas- 
ing variability — that  is,  an  increasing  "adapta- 
bility"— of  response.  An  increasing  adaptabil- 
ity of  the  responses  of  the  organism  to  the  con- 


58  THE  PHYSIOLOGY  OF  MIND 

stantly  changing  condition  of  its  existence  can 
only  become  possible  through  the  multiplica- 
tion of  intercalary  neurones.  This  multiplica- 
tion permits  alike  of  an  increased  complexity 
and  an  increased  adjustment  of  the  responses. 
Finally,  it  is  obvious  that  in  speaking  of  the 
function  of  the  end-brain,  the  cortex,  we  should 
speak  not  of  the  variability  of  the  responses,  but 
of  the  adaptation  of  the  responses. 

•  In  turn,  it  becomes  evident  that  the  responses 
of  the  end-brain,  the  telencephalon,  have  their 
origin  in  the  relation  which  its  neurones  bear  to 
those  of  the  primitive  segmental  brain,  to  the 
neurones  of  the  spinal  segments,  and  to  each 
other.  Transmission  into  the  end-brain  takes 
place  through  the  "between  brain,"  the  thal- 
amus. Here  we  find  that  through  the  develop- 
ment of  intercalary  neurones,  special  way  sta- 
tions, nuclei,  have  made  their  appearance.  In 
the  cells  of  the  latter  various  axones  bearing 
tactile,  visual,  auditory,  and  other  impacts  ter- 
minate synaptically ;  thence  other  axones  con- 
stituting the  so-called  "sensory  projection  fibers" 
pass  upward  to  the  cortex.  The  nuclei  in  the 
thalamus  which  play  this  role  of  way  stations — 
and  one  of  whose  functions  is  doubtless  that  of 


THE  PHYSIOLOGY  OF  tylIND  59 

reinforcement — are  spoken  of  as  "cortical  de- 
pendencies"; in  vertebrates  lacking  a  corre- 
sponding cortical  development  they  naturally 
have  no  existence.1 

Responses  make  their  exit  from  the  cortex  in 
axones  which  terminate  synaptically  not  in 
neurones  in  the  corpus  striatum  but  in  neurones 
in  the  brain  stem  and  spinal  segments.  The 
latter  group  of  axones  constitute  the  motor  pro- 
jection fibers  and  are  also  spoken  of  as  the  upper 
motor  pathway  or  pyramidal  tract.  Like  the 
nuclei  of  the  thalamus,  the  neurones  of  the 
corpus  striatum  doubtless  have  an  action  of  re- 
inforcement, but  it  is  probable  that  they  do 
much  more  than  this;  in  lower  vertebrates  their 
nuclear  arrangement  appears  to  be  such  as  to 
permit  of  relatively  complex  responses;  for  ex- 
ample, in  birds,  in  whom  the  striatum  is  large 
and  the  cortex  meagre.  In  higher  vertebrates 
they  appear  to  constitute  a  ready-made  mechan- 
ism (neurone  combinations)  for  various  auto- 
matic movements  controlled  or  inhibited  by  the 
cortex;  certain  it  is,  also,  that  the  corpus  stri- 
atum is  in  part  concerned  in  the  purely  dynamic 

1  All  of  the  afferent  impulses  save  those  coming  from  the  olfactory 
lobes  find  their  way  into  the  telencephalon  through  the  thalamus. 


60  THE  PHYSIOLOGY  OF  MIND 

function  of  the  maintenance  of  muscle  tone.  It 
is  clearly  evident  that  in  the  higher  vertebrates 
such  responses  as  have  their  origin  in  the  stri- 
atum or  are  transmitted  by  it  are  definitely 
fixed;  on  the  other  hand,  such  responses  as  arise 
in  the  cortex  and  are  transmitted  by  the  axones 
terminating  in  the  brain  stem  and  spinal  seg- 
ments are  variable  or  adaptable.  The  responses 
so  transmitted  are  adapted  to  the  environmental 
happenings.  They  are  the  resultants  of,  and, 
other  things  equal,  equivalent  to,  the  various 
and  multiple  impacts  received  by  the  organism. 
Having  established  the  avenues  of  ingress  and 
egress  and  having  considered  the  nature  of  the 
responses,  the  question  now  arises,  "What  takes 
place  in  the  cortex  itself?  The  sensory  projec- 
tion fibers  terminate  synaptically  in  certain  re- 
gions or  areas  of  the  cortex.  These  areas  are 
commonly  spoken  of  as  cortical  centers  for 
smell,  taste,  vision,  hearing,  tactile,  and  other 
impressions.  For  the  present  it  will  suffice  to 
regard  them  purely  as  gateways  or  avenues  of 
entrance  to  the  general  cortex.  Similarly,  the 
neurones  of  a  certain  area — that  of  the  ascend- 
ing frontal  convolution  in  man — give  rise  to 
axones  which  constitute  the  motor  projection 


THE   PHYSIOLOGY  OF  MIND  61 

fibers.  This  leaves  extensive  regions  which 
have  no  access  to  the  external  world  either  in 
the  way  of  receiving  impacts  or  of  transmitting 
them  save  through  such  connections,  direct  or 
indirect,  as  they  may  have  with  the  receiving  or 
the  emissive  areas.  The  facts  of  anatomical 
structure  show  that  there  are  extensive  and 
numerous  pathways — association  tracts — which 
connect  different  parts  of  the  cortex  with  each 
other.  Some  of  these  fibers  form  extensive  and 
long  bundles  or  fasciculi;  others  are  relatively 
short;  others  still  connect  immediately  or  closely 
adjoining  areas  of  the  cortex.  In  fact,  the 
arrangement  is  such  that  any  one  part  of  the 
cortex  is  directly  or  indirectly  connected  with 
every  other  part.  Finally,  extensive  commis- 
sural fibers  bring  about  an  intimate  union  of  the 
two  cerebral  hemispheres.  When  we  reflect  that 
the  human  cortex  contains  upwards  of  ten  thou- 
sand million  neurones1  and  that  each  neurone 
bears  numerous  dendrites  and  that  each  neu- 
rone sends  out  one  axone,  sometimes  two,  and 
several  collaterals,  all  terminating  in  numerous 
tuft-like  subdivisions,  we  can  realize  that  the 

1  According  to  Herrick,  loc.  cit.,  p.  27,  "some  9280  million,"  i.  e., 
approximately  10,000,000,000. 


62  THE  PHYSIOLOGY  OF  MIND 

number  of  possible  combinations  becomes  al- 
most infinite.  That  this  leads  to  great  "vari- 
ability" of  the  response,  or  to  restate  the  fact  in 
other  words,  to  great  possibilities  in  the  adapta- 
tion of  the  response  becomes  very  evident.  A 
given  adaptation,  as  we  will  see  later,  is  the 
resultant  of  the  impacts  received  and  of  the 
previously  existing  cortical  neuronic  combina- 
tions. Finally,  the  conclusion  is  inevitable  that 
the  response  to  the  impacts  must  be  automatic. 
Such  response  is  clearly  automatic  when  but 
one  neurone  is  interposed  between  a  receptor 
and  an  effector,  and  the  factors  do  not  change 
when  the  interposed  neurone  becomes  multiple. 

A  further  fact  now  becomes  apparent,  namely, 
that  as  a  result  of  a  given  impact  a  very  large 
number  of  neurones  may  and  probably  do  be- 
come involved  in  the  transmission;  the  trans- 
mission doubtless  takes  place  not  only  through 
many  hundreds,  but  through  many  thousands 
of  cortical  neurones.  In  the  course  of  the 
transmission  a  gateway  of  exit  is  finally  reached, 
and  thence  a  response  is  transmitted  via  the 
brain  stem  or  cord  to  the  effectors. 

Another  inference  now  presents  itself,  an  in- 
ference unavoidable  and  conclusive,  and  which 


THE  PHYSIOLOGY  OF  MIND  63 

is  of  the  very  greatest  importance;  and  that  is, 
if  the  response  is  'Variable,"  if  it  is  "adjust- 
able," and  therefore  capable  of  change,  the  neu- 
rones of  the  cortex  cannot  bear  the  same  fixed 
relations  to  each  other  as  do  the  neurones  of  the 
brain  stem  and  cord. 

Many  years  ago — in  1895 — in  thinking  over 
the  problems  presented  by  hysteria,  it  occurred 
to  the  writer  that  possibly  a  hysterical  paralysis 
— e.  g.,  of  an  arm — could  be  accounted  for  by  a 
retraction  of  the  processes  of  the  neurones  in 
the  "arm  center"  of  the  motor  area  of  the  cor- 
tex, so  that  these  neurones  would  no  longer  be 
in  physiological  relation  with  the  rest  of  the  cor- 
tex. In  other  words,  it  occurred  to  the  writer 
that  possibly  the  neurones  of  the  cortex  had 
some  power  of  movement  as  far  as  their  ter- 
minal processes,  the  dendrites,  and  end-tufts  are 
concerned;  so  that  the  latter  could  in  some  de- 
gree be  retracted  or  extended.  An  examination 
of  the  literature  revealed  that  the  idea  of  move- 
ment on  the  part  of  the  neurone  had  already 
occurred  to  three  other  writers,  one  in  Germany 
and  two  in  France.  The  first  to  advance  such  a 
view    was    Rabl-Riickard,1    who    in    1890    sug- 

1  Rabl-Riickard,  Neuro!og.  Centralblatt,  April,  1890,  p.  199. 


64  THE  PHYSIOLOGY  OF  MIND 

gested  that  nerve-cells  have  an  amceboid  move- 
ment; and  he,  at  the  same  time,  pointed  out  the 
significance  of  such  a  view  in  enabling  us  to 
explain  the  mechanism  of  psychic  processes. 
His  ideas  attracted  no  attention,  but  in  1894 
Lepine,1  in  a  paper  on  a  case  of  hysteria  of  a 
peculiar  form,  advanced  practically  the  same 
theory.  His  idea  was  that  the  neurones  were 
capable  of  movement,  and  to  such  an  extent  as 
to  enable  them  to  alter  the  degree  of  their  rela- 
tion to  each  other.  Some  six  months  after- 
wards another  French  writer,  Mathias  Duval,2 
advanced  the  same  theory  in  a  communication 
made  to  the  Societe  de  Biologic  Lepine  had 
been  unaware  of  the  theory  advanced  by  Rabl- 
Rlickard  and  Mathias  Duval,  and  was  equally 
unaware  of  the  views  advanced  by  Lepine.  A 
week  after  Duval  had  advanced  his  theory, 
Lepine,3  before  the  same  society,  repeated  his 
former  arguments  in  its  support.  I  myself  pre- 
sented the  theory  of  the  movement  of  the  neu- 
rone in  a  paper  read  before  the  College  of  Phys- 
icians of  Philadelphia  in  January,  1896,4  and  in 

1  Lepine,  Revue  de  Medecine,  Aout,  1894,  p.  713. 

2  Duval,  Comptes  Rendus  de  la  Societe  de  Biologie,  Fevrier,  1895, 
pp.  74,  86. 

3  Lepine,  Comptes  Rendus  de  la  Societe  de  Biologie,  1895,  p.  85. 

4  Trans.  College  of  Physicians,  Philadelphia,  1896. 


THE   PHYSIOLOGY  OF  MIND  65 

June  of  that  year  read  an  address  on  the  same 
subject  before  the  American  Neurological  Asso- 
ciation.1 In  the  meantime,  in  the  spring  of 
1896,  the  theory  had  been  again  advanced  by 
two  other  French  physicians,  Azoulay  and 
Pupin.  This  view  was  not  accepted  by  Ramon 
y  Cajal.2  He,  however,  saw  the  necessity  of  ad- 
mitting a  change  in  the  relations  of  the  neurones 
to  each  other,  and  offered  the  explanation  that 
it  was  the  neuroglia  cells  which  moved  and  not 
the  neurones.  He  maintained  that  the  processes 
of  the  neuroglia  cells  represent  an  insulating  and 
non-conducting  material,  and  that  during  the 
stage  of  relaxation  these  processes  penetrate 
between  the  arborizations  of  the  nerve-cells  and 
so  make  difficult  or  impossible  the  passage  of 
nerve  currents;  on  the  other  hand,  in  the  stage 
of  contraction  the  processes  of  the  neuroglia 
cells  are  retracted  and  they  then  no  longer  sepa- 
rate the  processes  of  the  nerve-cells,  and  the 
latter  are  thus  permitted  to  come  into  contact. 
Evidently  Ramon  y  Cajal  admitted  the  very 
thing  against  which  he  contended,  for  if  the 
nerve-cell  processes  are  at  one  time  not  in  con- 

1  Trans.  Amer.  Neur.  Assoc,  August,  1896. 

2  Ramdn  y  Cajal,  Revista  de  Medicina  y,  Cirugia  Practicas,  Mayo, 
5,  1895,  p.  497. 

5 


66  THE  PHYSIOLOGY  OF  MIND 

tact  and  at  another  are  in  contact,  they  cer- 
tainly move.  It  matters  not  whether  the  mo- 
tion is  an  active  or  a  passive  one.  Finally,  while 
movements  of  neurones  have  not  been  observed 
in  vertebrates,  one  very  suggestive  observation 
was  made  in  1890  by  Wiedersheim.1  He  saw  in 
the  living  animal,  an  entomostracan,  leptodora 
hyalina,  the  nerve-cells  in  the  oesophageal  gan- 
glion move.  The  oesophageal  ganglion  may  in 
a  sense  be  regarded  as  the  brain  of  the  animal, 
inasmuch  as  it  receives  the  fibers  of  the  optic 
nerve,  and  Wiedersheim  actually  saw  these  cells 
move  and  change  their  shape.  He  described  the 
movement  as  slow  and  flowing,  and  pictures  in 
his  paper  the  various  shapes  assumed  by  the 
nerve-cells  at  different  times.  While  it  is  a  far 
cry  from  the  nerve-cells  of  invertebrate  forms  to 
those  of  the  vertebrates,  the  nerve-cells  of  the 
former,  the  protoneurones,  illustrate,  as  we  have 
seen,  elemental  truths,  and  the  observation  of 
Wiedersheim  is  in  harmony  with  the  view  that 
the  relations  of  the  primordial  neurones  are  not 
fixed  as  we  find  them  in  the  segments  of  the  cord 
and  brain  stem  of  vertebrates,  but  permit  of 
change  with  each  other.     It  would  appear  that 

1  Wiedersheim,  Anatomiseher  Anzeiger,  1890,  p.  693. 


THE  PHYSIOLOGY  OF  MIND  67 

this  motility  or  facility  of  change  lost  in  the 
cord  and  brain  stem  has  been  preserved  in  the 
telencephalon. 

Further,  we  are  so  in  the  habit  of  looking  at 
nerve-cells  in  mounted  and  stained  sections  of 
the  cord  and  brain  that  we  are  apt  to  transfer 
the  idea  of  fixation  of  structure  subconsciously 
to  our  conceptions  of  the  living  cells  and  pro- 
cesses, and  to  overlook  some  of  the  marvelous 
truths  which  they  present.  The  neurone  has 
its  origin  in  a  simple  undifferentiated  cell,  the 
neuroblast;  in  the  course  of  its  development  it 
sends  out  processes,  some  of  them  of  enormous 
length,  which  in  their  growth  often  pass  along 
devious  routes  to  a  definite  destination.  For 
instance,  certain  cells  of  the  motor  area  of  the 
cortex  send  forth  processes,  the  axones,  which 
grow  through  great  distances  to  come  finally 
into  relation  with  neurones  in  definite  segments 
of  the  spinal  cord;  and  again,  other  neurones, 
both  motor  and  sensory,  send  out  processes 
which  bring  the  various  portions  and  areas  of 
the  body  into  definite  relations  with  them;  that 
is,  the  axones  grow  out  until  they  reach  definite 
effectors  or  definite  end-organs  of  the  body  sur- 
face   and    elsewhere.      That    this    phenomenon 


68  THE  PHYSIOLOGY  OF  MIND 

must  be  the  expression  of  purely  physical  or 
chemical  causes  there  can  be  no  doubt.  Defi- 
nite causes  must  be  at  work,  such,  for  instance, 
as  determines  the  growth  of  the  roots  of  plants 
toward  water.  "Many  organs  of  the  adult  body 
are  known  to  secrete  specific  soluble  chemical 
substances  termed  'hormones,'  which  diffuse 
throughout  the  lymph  or  blood  and  call  forth 
functional  activity  in  remote  organs.  It  is  pos- 
sible that  during  development  of  the  body,  the 
organs,  as  soon  as  definite  stages  of  growth  are 
reached,  secrete  similar  substances  which  diffuse 
through  the  surrounding  tissue  and  each  of  which 
has  a  chemotactic  affinity  for  a  certain  type 
of  developing  neurones.  Thus,  the  developing 
muscles  may  secrete  a  substance  to  which  the 
motor  neurones  of  the  spinal  cord  react  by  a 
growth  of  their  embryonic  axones  toward  the 
source  of  the  stimulating  material."1  This  phe- 
nomenon is  known  as  chemotaxis.  The  thought 
also  suggests  itself  that  possibly  this  process 
does  not  cease  absolutely  with  the  evolution  of 
the  organism,  but  in  some  measure  continues  in 
the  fully  developed  organism  in  accordance  with 
changing  conditions. 

1  See  Herrick,  loc.  cit.,  pp.  Ill,  112. 


THE   PHYSIOLOGY  OF  MIND  69 

Again,  it  has  been  found  that  in  the  course  of 
the  evolution  of  vertebrate  forms  nerve-cells 
change  their  positions.  Numerous  groups  of 
cell  bodies  with  specific  functions  move  from 
their  primitive  positions  to  new  locations.  Our 
knowledge  of  their  migrations  is  due  mainly  to 
Kappers.  It  would  seem  that  cell  bodies  "tend 
to  migrate  in  the  direction  from  which  they 
habitually  receive  their  stimuli,  i.  e.,  in  the 
direction  taken  by  their  dendrites.  If  there  is 
a,  change  in  the  direction  from  which  a  given 
nucleus  (i.  e.,  a  group  of  cells)  receives  its  chief 
stimuli,  the  nucleus  as  a  whole  will  tend  to 
move  toward  the  new  source  of  excitation  and 
away  from  the  old.1  The  change  in  position  is 
obviously  expressive  of  a  physical  reaction  to  a 
stimulus,  and  the  phenomenon  has  received  the 
name  of  "neurobiotaxis."  Both  the  facts  of 
chemotaxis  and  neurobiotaxis  throw  an  inter- 
esting light  on  the  active,  living,  growing  char- 
acter of  the  neurone;  changing  and  capable 
of  change.  Indeed,  capacity  for  change  and 
adaptation  seems  inherent  in  the  primitive 
neuroblast.  At  times  continuous  changes  and 
fresh  adaptations  may  be  the  result;  at  others, 

2  See  Herrick,  loc.  cit.,  p.  112. 


70  THE  PHYSIOLOGY  OF  MIND 

fixation    or    relative    fixation    may    be    estab- 
lished. 

Let  us  again  turn  our  attention  to  the  rela- 
tions between  the  neurones,  i.  e.,  to  the  synapses. 
Kappers1  points  out  that  the  relations  of  neu- 
rones to  each  other  vary  somewhat.  In  some 
the  relation  may  be  practically  one  of  con- 
tinuity, as  when  the  neurofibrils  of  one  neurone 
pass  directly  into  those  of  the  second;  as  is  often 
the  case  in  the  vestibular  apparatus.  Such  an 
arrangement  may  be  expected  in  the  Mauthner 
cell  in  the  catfish — a  large  cell  in  relation  with 
the  vestibular  nerve — in  which  transmission 
probably  takes  place  directly  between  the  ax- 
ones  of  one  cell  and  the  dendrites  of  another. 
Between  other  cells  the  relation  may  be  merely 
that  of  contiguity  or,  it  may  be  added,  of 
propinquity.  At  the  time  of  the  passage  of  a 
reflex  a  delay  in  transmission  occurs  at  a  syn- 
apse. Kappers  thinks  that  differences  in  delay 
may  be  due  to  differences  in  the  synapses. 
Probably  this  delay  is  greater  when  the  his- 
tological relation  consists  merely  of  contiguity 
and  greatest  when  this  contiguity  or  approxi- 

1  Kappers,  Versuch  einer  Erklarung  des  Verhaltens  an  der  Synapsis, 
Psych,  en  Neurol.,  Bladen,  1917,  H.  6,  p.  440;  also  Brain,  July,  1921, 
p.  125. 


THE  PHYSIOLOGY  OF  MIND  71 

mation  must  first  be  established.  The  last 
would  naturally  result  when  a  new  pathway 
was  being  formed,  or  in  the  case  of  one  that  was 
only  occasionally  used.  Kappers  regards  the 
transmission  through  the  neurone  in  one  direction 
only — i.  e.,  the  polarization  of  the  neurone — 
as  a  neurobio tactic  phenomenon.  He  declares 
that  the  formation  of  dendrites  and  axones  is 
the  result  of  the  reaction  to  stimuli;  the  axone 
is  a  formed  product  of  the  stimuli  current;  it 
grows  with  the  current,  is  formed  by  the  cur- 
rent. The  dendrite  is  likewise  a  formed  product 
of  the  stimuli  current.  In  the  passage  of  the 
current  from  cell  to  cell,  the  axone  terminals  of 
the  first  cell  are  drawn  toward  the  dendrites  of 
the  second  cell,  and  the  dendrites  of  the  second 
cell  are  drawn  toward  the  axone  terminals  of 
the  first.  The  mere  act  of  the  transmission  of 
an  impulse  brings  about  an  approach,  the  whole 
process  being  neurobiotactic. 

Sherrington1  regarded  it  as  improbable  that 
the  phenomena  of  the  synapse  are  dependent 
upon  an  amceboidism  of  the  neurones,  and  he 
did  so  for  the  following  reason:  The  length  of 
the  delay  caused  in  a  reflex  by  a  synapse—^'.  e.> 

1  Sherrington,  The  Integrative  Action  of  the  Nervous  System,  1911,  p.  24. 


72  THE  PHYSIOLOGY  OF  MIND 

the  latent  period — is  inversely  proportional  to 
the  intensity  of  the  reflex.  Sherrington  found 
that  if  the  latent  period  of  a  reflex  produced  by 
delivery  of  the  stimulus  in  its  full  strength  be 
compared  with  the  latent  period  of  the  reflex 
produced  in  two  stages — i.  e.,  by  an  "initial" 
stimulus  and  an  "incremental"  stimulus — the 
latent  period  resulting  in  the  two  stimuli  reflex 
is  longer  than  in  the  first,  namely,  when  only 
one  maximal  stimulus  is  applied.  This  result 
he  regarded  as  an  argument  against  an  amoeboid 
movement  on  the  part  of  the  neurones;  a  bridge 
once  having  been  constructed  by  the  initial 
stimulus,  there  should  be  no  additional  loss  of 
time.  However,  Sherrington's  results  also  showed 
that  the  latent  period  of  the  incremental  stim- 
ulus is  always  shorter  than  that  of  the  initial 
stimulus.  As  Kappers  points  out,  this  fact  can 
only  be  explained  by  supposing  that  something 
takes  place  as  a  result  of  the  initial  stimulus 
which  does  not  take  place  as  a  result  of  the  in- 
cremental stimulus;  and  to  Kappers  there  seems 
no  good  reason  for  supposing  that  the  added 
time  of  the  initial  latent  period  is  not  con- 
sumed by  the  approach  of  the  colloidal  particles 
of   the   terminal   processes.      Kappers   declares 


THE   PHYSIOLOGY   OF  MIND  73 

that  the  amoeboidism,  and,  in  any  case,  the 
neurobiotactic  phenomena  of  nerve-cells,  have 
not  for  a  long  time  been  mere  hypotheses,  but 
are  actual  facts. 

The  interrelations  of  the  neurones  have  been 
the  subject  of  much  speculative  thought  and 
study.  Sherrington  who,  as  just  seen,  denies  the 
amoeboidism  of  the  neurone,  expresses  himself 
as  follows:1  "At  the  nexus  between  cells,  if 
there  be  not  actual  confluence,  there  must  be  a 
surface  of  separation.  At  the  nexus  between 
efferent  neurone  and  the  muscle-cell,  electrical 
organ,  etc.,  which  it  innervates,  it  is  generally 
admitted  that  there  is  not  actual  confluence  of 
the  two  cells  together,  but  that  a  surface  sepa- 
rates them;  and  a  surface  of  separation  is  phys- 
ically a  membrane." 

"If  the  conductive  element  of  the  neurone  be 
fluid,  and  if  at  the  nexus  between  neurone  and 
neurone  there  does  not  exist  actual  confluence 
of  the  conductive  part  of  one  cell  with  the  con- 
ductive part  of  the  other — e.  g.,  if  there  is  not 
actual  continuity  of  physical  phase  between 
them — there  must  be  a  surface  of  separation. 
Even  should  a  membrane  visible  to  the  micro- 

1  See  Sherrington,  loc.  cit.,  pp.  16,  17. 


74  THE  PHYSIOLOGY  OF  MIND 

scope  not  appear,  the  mere  fact  of  non-con- 
fluence of  the  one  with  the  other  implies  the 
existence  of  a  surface  of  separation.  Such  a 
surface  might  restrain  diffusion,  bank  up  os- 
motic pressure,  restrict  the  movement  of  ions, 
accumulate  electric  charges,  support  a  double 
electric  layer,  alter  in  shape  and  surface  tension 
with  changes  in  difference  of  potential,  alter  in 
difference  of  potential  with  changes  in  surface 
tension  or  in  shape,  or  intervene  as  a  membrane 
between  dilute  solutions  of  electrolytes  of  dif- 
ferent concentration  or  colloidal  suspensions 
with  different  sign  of  charge." 

Regarding  this  hypothetical  membrane  Kap- 
pers  is  of  the  opinion  that  by  a  synaptic  mem- 
brane we  need  not  understand  an  actual  mem- 
branous structure,  but  "merely  an  electro- 
endosmotic  layer."  Again,  obviously  such  a 
membrane  if  morphologically  demonstrable 
would  consist  of  the  apposition  or  fusion  of 
two  cell  walls  and,  further,  the  physical  prin- 
ciples involved — endosmosis  and  the  possible 
passage  of  electrically  charged  ions — would 
apply  especially  to  neurones  with  fixed  synaptic 
relations  and  perhaps  in  less  degree  to  neurones 
whose  relations  were  changeable.    In  any  event, 


THE  PHYSIOLOGY  OF  MIND  75 

it  is  quite  probable  that  the  physical  principles 
involved  would  not  differ  in  essence  from  those 
that  determine  the  approach  of  the  pseudopod 
of  an  amoeba  to  a  nitrogenous  or  other  food 
particle. 

Leaving  for  the  time  being  the  consideration 
of  this  "electro-endosmotic  layer"  or  synaptic 
"membrane"  and  the  consideration  of  the  phys- 
ical or  chemical  principles  involved,  let  us  turn 
our  attention  once  more  to  the  reactions  of 
the  cortical  neurone,  the  neurone  of  the  telen- 
cephalon, to  the  stimuli,  the  impacts,  trans- 
mitted to  it  from  the  segmental  brain.  In  one 
of  my  earlier  papers,  read  before  the  American 
Neurological  Association  in  June,  1896,  I  thus 
expressed  myself:1 

"A  sequence  of  sound  vibrations  impinging 
upon  the  peripheral  auditory  neurones  pro- 
duces in  them  a  change,  which  in  turn  affects 
the  relations  which  their  neuraxones  bear  to 
the  auditory  nuclei,  and  secondarily  to  the 
auditory  cortical  neurones.  Not  only  are  the 
latter  affected  by  the  impressions  received  from 
the  afferent  neuraxones,  but  they,  in  turn,  re- 

1  Dercum,  Presidential  Address  delivered  before  The  American 
Neurological  Association  (The  Functions  of  the  Neurone),  The  Journal 
of  Nervous  and  Mental  Disease,  Vol.  XXI,  No.  8,  1896,  p.  522. 


76  THE  PHYSIOLOGY  OF  MIND 

act  in  such  a  way  as  to  change  their  relations 
to  each  other,  and  the  new  positions  assumed 
by  them  will  depend  largely  upon  the  fact  as  to 
whether  a  similar  sequence  of  impressions  has 
passed  through  them  before.  If  so,  the  old 
combinations  will  be  re-formed.  From  the 
cortical  auditory  center  there  now  pass  through 
the  general  cortex  a  series  of  combinations 
among  the  neurones,  also  along  the  oldest  and 
best-travelled  lines,  so  that  a  given  sequence  of 
musical  sounds  may  suggest  at  first  a  familiar 
air,  a  moment  later  a  vivid  recollection  of  an 
opera  once  heard  and  seen.  In  this  simple  il- 
lustration is  embraced  the  physiology  of  per- 
ception, of  conception,  of  memory,  and  the  ex- 
planation of  the  very  sequence  of  thought 
itself." 

Setting  aside  for  the  time  being  the  dis- 
cussion of  the  factors  of  sensation  and  of  con- 
sciousness embraced  in  the  above^  interpreta- 
tion, let  us  take  up  more  in  detail  the  various 
other  phenomena  presented.  First,  we  are  im- 
pressed by  the  fact  that  time  is  consumed  in 
the  transmission  of  the  impact  from  the  moment 
of  its  reception  until  it  finds  motor  expression. 
This  is  known  as  the  reaction  time.    We  have 


THE  PHYSIOLOGY  OF  MIND  77 

already  briefly  considered  the  delay  which  occurs 
at  a  synapse.  It  appears  to  be  time  consumed 
in  the  preparation  of  the  synapse  for  trans- 
mission, i.  e.,  in  the  "setting"  of  the  synapse 
(to  use  Sherrington's  term),  and  which  con- 
sists possibly  in  the  formation  of  protoplasmic 
extensions,  in  the  passage  of  ions,  or  in  the 
establishment  of  induction.  Many  studies  have 
been  made  as  to  the  time  lost  in  the  passage 
through  gray  matter  of  various  reflexes,  and  it 
would  appear  that  the  simpler  the  reflex,  the 
shorter  the  reaction  time,  and  the  more  complex 
the  reflex  or  response,  the  longer  the  reaction 
time;  thus  a  simple  spinal  reflex  in  the  frog  re- 
veals a  loss  of  0.008  second  (Wundt)  or  0.014 
and  0.021  second  (Buchanan),  while  the  sim- 
plest reaction  times  measured  in  the  psycholog- 
ical laboratories  vary  between  0.1  and  0.2  sec- 
ond,1 and  the  reaction  times  as  measured  by 
physicians  between  a  "stimulus  word"  and  a 
"reaction  word"  range  from  one  to  two  seconds 
and  sometimes  longer.  The  time  consumed  is 
evidently  lost  in  some  physical  process,  as  al- 
ready indicated.  The  transmission  of  impact 
from  neurone  to  neurone  means  the  overcoming 

1  See  Herrick,  loc.  cit.,  p.  104. 


78  THE  PHYSIOLOGY  OF  MIND 

of  inertia  or  resistance  at  the  beginning  of  each 
neurone,  i.  e.,  at  its  dendrite.  Each  synapse,  so 
to  speak,  presents  a  new  "neurone  threshold" 
(Sherrington). 

The  positions  of  neurones  and  their  relations 
to  each  other  are,  as  we  have  seen,  determined 
by  the  principle  of  neurobiotaxis.  According  to 
the  latter,  the  dendrites  are  directed  or,  rather, 
are  drawn  toward  the  sources  of  stimulation, 
i.  e.,  the  sources  from  which  the  impacts  are  re- 
ceived; the  axones  likewise  are  drawn  toward 
the  dendrites  of  the  succeeding  cell  and,  in 
given  instances,  in  the  course  of  phylogeny 
even  the  entire  neurone  may  move.  Here  we 
are  concerned,  however,  merely  with  the  be- 
havior of  the  dendrites  and  axone  terminals. 
No  doubt  the  transmission,  the  diffusion,  of  an 
impact,  to  definite  neurones,  is  determined  by 
neurobiotactic  principles,  and  in  this  is  to  be 
found  the  explanation  of  "association."  In 
their  early  phylogenetic  relationships  the  trans- 
mission of  impact  from  neurone  to  neurone  was 
doubtless  determined  by  propinquity,  and  in  the 
multiplication  of  intercalary  neurones  there 
gradually  appeared  the  "common  paths"  (see 
p.  48).     Definite  groups  of  neurones,  therefore, 


THE  PHYSIOLOGY  OF  MIND  79 

became  associated  in  the  transmission  of  given 
impacts,  e.  g.,  of  sound,  as  in  the  illustration 
quoted  above.  The  transmission  did  not,  how- 
ever, cease  in  the  so-called  cortical  center  for 
hearing  in  the  temporal  lobe,  but  was  trans- 
mitted along  "association"  paths  to  other  re- 
gions of  the  brain.  What  determines  the  direc- 
tion of  the  transmission?  Why  do  the  impacts 
break  through  definite  thresholds  and  thus  give 
rise  to  certain  associations?  Doubtless  the 
tendency  in  the  primitive  nervous  system  was 
to  a  general  diffusion  of  impacts,  but  auto- 
matically, as  in  the  instance  of  the  establish- 
ment in  the  fish  of  the  common  effector  paths 
concerned  in  swimming  as  a  result  of  the  com- 
mon action  of  the  receptors  of  smell,  sight,  and 
hearing  in  determining  the  approach  of  the  fish 
to  food  (see  p.  54),  so  impacts  entering  the 
cortex  by  way  of  the  organ  of  hearing  would 
probably  diffuse  more  readily  toward  the  cor- 
tical areas  for  vision  than  to  those  of  touch, 
smell,  or  taste;  as  in  the  higher  vertebrates, 
impacts  of  sight  and  sound  from  a  given  source 
are  very  frequently  simultaneous.  That  there 
should  be  a  lowering  of  thresholds  between  si- 
multaneously aroused  groups  of  neurones  would 


80  THE  PHYSIOLOGY  OF  MIND 

naturally  follow.  Activity  of  neighboring  groups 
of  neurones  would  necessarily  mean  an  in- 
creased amceboidism.  If  one  group  only  be 
aroused,  pathways  having  once  been  established, 
there  would  be  a  transmission  to  the  others 
which  were  still  quiescent.  At  any  rate,  what- 
ever be  the  explanation,  it  can,  I  think,  be 
safely  assumed  that  association — i.  e.,  trans- 
mission to  other  neurones — takes  place  in  ac- 
cordance with  physical  principles,  and,  second, 
having  once  taken  place,  they  take  place  more 
and  more  readily  with  repetition.  In  other 
words,  to  use  a  physiological  term,  they  be- 
come "facilitated." 

The  special  trend  followed  by  the  cortical 
neurones  in  their  transmission-associations 
doubtless  depends  upon  a  number  of  factors. 
If  the  experiences  are  old  and  often  met  with, 
the  same  or  similar  associations  are  repeated; 
if  they  are  new  experiences,  no  doubt  new  com- 
binations are  formed,  new  pathways  estab- 
lished. It  is  probably  this  quality  of  neurone 
activity  which  makes  possible  additions  to  our 
knowledge;  it  becomes  thus  the  basis  of  all 
training  and  education. 

However,  the  function  of  the  neurone  of  the 


THE   PHYSIOLOGY  OF  MIND  81 

cortex  is  not  merely  that  of  transmission.  The 
reception  of  the  impact  means  not  only  the 
passage  of  the  latter  through  dendrites,  cell 
body  and  axone,  but  also  a  change  in  the  sub- 
stance of  the  neurone;  a  change  physical  and 
chemical  which  results  in  the  evolution  of 
energy.  An  active  consumption  of  substance, 
probably  the  result  of  an  increased  oxidation, 
takes  place,  and  a  corresponding  amount  of 
energy  is  added  to  the  impulse  transmitted.  It 
is  easy  to  understand  that  when  the  latter  finally 
reaches  the  effectors — i.  e.,  finds  motor  expres- 
sion— it  may  differ  greatly  both  in  amount  and 
character  from  that  originally  impinging  upon 
the  receptors.  A  very  small  stimulus  may 
liberate  a  large  amount  of  energy.  Each  neu- 
rone is  a  storehouse  of  energy  which  needs  but 
the  transmitted  tap  of  the  impact  to  release  it. 
Evidently  a  series  of  neurones  in  relation  with 
a  receptor  will  intensify  the  impressions  im- 
pinging upon  the  latter.  Such  an  arrangement 
is  especially  evident  in  the  olfactory  lobe  and 
doubtless  accounts  for  the  recognition  by  the 
organism  of  impacts  so  excessively  minute  as 
are  those  which  impinge  upon  the  olfactory  re- 
ceptors.   Ramon  y  Cajal  has  in  this  connection 


82  THE  PHYSIOLOGY  OF  MIND 

employed  the  expression  "avalanche  conduc- 
tion." Doubtless  a  similar  truth  obtains  in  re- 
gard to  the  intercalary  neurones  next  in  series. 
i.  e.,  those  concerned  primarily  in  the  central 
transmission  of  the  impact,  and  also  and 
finally,  in  regard  to  those  in  relation  with  the 
effectors. 

That  the  impact  in  its  course  of  transmission 
through  the  various  neurones — avalanche  con- 
duction or  other — undergoes,  in  addition,  con- 
versions in  character,  is  modified,  transformed 
into  different  equivalents  is  probably  equally 
true;  but  the  discussion  of  this  interesting  ques- 
tion is  deferred  for  the  present.  One  truth, 
however,  remains  apparent,  and  that  is  that 
the  10,000  million  intercalary  neurones  of  the 
cortex  add  merely  to  the  complexity  of  the  re- 
sponse; the  purely  physical,  automatic  char- 
acter of  the  latter  remains  unchanged.  This 
automatism  is  as  true  of  the  higher  vertebrates 
as  it  is  of  the  lower.  The  reaction  of  the  fish 
to  the  environment  is  clearly  automatic  (see 
p.  54),  and  the  development  of  the  telencephalon 
merely  makes  that  automatism  more  complex. 

A  discussion  which  can  no  longer  be  deferred 
is  that  of  consciousness.     In  a  consideration  of 


THE  PHYSIOLOGY  OF  MIND  83 

nervous  phenomena,  the  problem  of  conscious- 
ness of  necessity  obtrudes  itself,  and,  although 
in  a  study  of  the  simple  problems  it  may  be 
ignored,  it  must  finally  be  squarely  faced. 
When  we  turn  our  attention  to  the  protozoa  and 
more  especially  to  the  amoeba,  we  realize  at 
once  that  a  discussion  whether  such  an  organ- 
ism is  conscious,  whether  it  has  sensation, 
feeling,  a  sense  of  being,  becomes  futile. 
We  have  seen  reason  to  believe  (see  pages 
12,  14)  that  the  reactions  of  the  amceba  to 
the  environment,  like  that  of  the  white  blood- 
corpuscles  and  the  other  individual  cells  of  the 
metazoa,  are  due  to  purely  physical  and  chem- 
ical causes.  If  such  structures  have  a  sense  of 
being,  it  must  be  one  that  is  shared  by  the  sub- 
stance and  energy  of  the  universe  generally;  in- 
deed, it  must  be  participated  in  by  that  ulti- 
mate expression  of  substance  and  energy,  the 
electron  itself.  Are  we  to  infer  that  "senti- 
ency"  makes  its  appearance  when  the  combina- 
tion of  a  given  number  of  amino-acids  results 
in  the  formation  of  a  substance  that  is  the  seat 
of  a  continuous  chemical  change  featured  by  a 
simultaneous  upbuilding  and  reduction  (see  p. 
40),  a  continuous  change  that  is  itself  a  direct 


84  THE   PHYSIOLOGY  OF  MIND 

result  of  its  reaction  to  its  environment?  or,  are 
we  to  defer  this  conception  of  sentiency  until 
special  arrangements  for  the  reception  and  trans- 
mission of  impacts  make  their  appearance?  The 
difficulty  increases  when  we  approach  the  more 
complex  metazoa.  In  the  contemplation  of  the 
ccelenterates  we  may  be  content  to  set  aside  the 
question  of  "feeling,"  but  are  we  justified  in 
doing  this  in  the  case  of  insects  with  their 
obviously  complex  sense  organs  and  central 
nervous  aggregations?  Again,  are  we  justified 
in  assuming  that  the  cuttlefish  in  spite  of  his 
elaborate  eye  does  not  "see,"  has  not  "light 
sensation"  of  some  kind  or  other?  Assuredly  it 
is  unphilosophical  to  assume  that  the  fish  in 
spite  of  its  enormous  olfactory  brain  does  not 
"smell,"  or  being  possessed  of  eyes  and  ears, 
that  it  does  not  "see,"  does  not  "hear."  True, 
the  impacts  received  by  the  "nose  brain,"  the 
"eye  brain,"  the  "ear  brain,"  and  the  "skin 
brain"  are  all  transmitted  into  the  common 
paths  concerned  in  swimming,  i.  e.,  in  bringing 
about  automatic  approach  to  or  withdrawal 
from  objects  in  the  water;  yet,  though  the  "eye 
brain"  may  glow  with  the  sensation  of  light  and 
the  "ear  brain"  ring  with  the  sensation  of  sound, 


THE  PHYSIOLOGY  OF  MIND  85 

the  consciousness  of  the  fish  must  be  something 
very  different  from  that  experienced  by  our- 
selves. In  what  does  this  difference  consist? 
Evidently  it  concerns  the  function  of  the  telen- 
cephalon. 

Let  us  for  the  time  being  turn  our  attention 
to  the  responses  to  impacts  in  the  higher  ver- 
tebrates. In  amphibians  the  situation  has 
changed  but  little  from  that  in  fishes;  the  re- 
sponses are  still  the  invariable,  non-adjustable 
responses  of  a  segmental  brain.  The  same  may 
be  said  of  reptiles;  variable  or  adjustable  re- 
sponses are  negligible  factors.  When  we  turn 
to  birds,  the  situation  has  apparently  slightly 
changed.  In  addition  to  their  very  remarkable 
and  complex  automatic  "instinctive"  responses, 
there  appears  to  be  a  capacity,  though  an  ex- 
ceedingly limited  one,  for  adjustable  responses. 
In  birds  the  pallium — the  cortex  of  the  telen- 
cephalon— is  still  very  rudimentary,  and  if  the 
bird  does  any  "thinking"  he  must  do  it  with 
his  thalamus  and  striatum.  That  he  does  very 
little  is  quite  evident  from  the  behavior  of  birds 
ordinarily;  that  he  exceptionally  does  some  is 
equally  evident  from  the  occasional  behavior  of 
certain  birds,  e.  g.,  the  parrot.     Further,  it  is 


86  THE  PHYSIOLOGY  OF  MIND 

exceedingly  probable,  as  we  shall  see  later  on, 
that  the  complex  instincts  of  birds,  as  well  as 
those  of  mammals,  had  their  origin  in  adjustable 
responses. 

It  would  appear  that  the  structures  of  the 
primitive  brain,  the  palseo-encephalon,  the  seg- 
mental brain,  as  we  term  it,  is  of  such  a  char- 
acter as  to  permit  of  adjustable  responses  in 
only  a  limited  degree.  However,  that  such  ad- 
justable responses  did  take  place  in  it  originally 
and  still  do  take  place  in  it  in  birds  and  per- 
haps in  lower  forms,  though  in  very  small 
measure,  is  exceedingly  probable.  In  mam- 
mals, however,  the  function  of  the  segmental 
brain,  like  that  of  the  spinal  cord,  is  limited  to 
non-adjustable  responses.  Like  the  spinal  cord, 
the  segmental  brain  has  been  reduced  to  a  fixed 
mechanism.  Such  capacity  for  variable  or  ad- 
justable responses  as  it  may  have  originally 
possessed  has  been  usurped  by  the  telencephalon. 

Whatever  may  be  the  state  of  consciousness 
in  vertebrates  other  than  mammals,  it  is  quite 
certain  that  in  the  latter  fixed  responses  play  no 
r61e  in  consciousness;  this  is  true  of  the  re- 
sponses in  the  spinal  cord,  and  it  is  doubtless 
equally  true  of  the  responses  in  the  segmental 


THE  PHYSIOLOGY  OF  MIND  87 

brain.  Here  again  the  telencephalon  has  played 
the  role  of  usurper,  for  the  function  of  con- 
sciousness, as  we  know  it,  is  limited  to  the 
telencephalon. 

When  we  now  turn  our  attention  to  this 
function  of  the  telencephalon,  the  following  in- 
teresting facts  and  inferences  present  them- 
selves. To  begin,  various  acts  themselves  the 
outward  expression — the  effector  result — of  the 
intercalary  function  of  the  telencephalon,  and 
which  when  first  performed  are  attended  by 
consciousness,  may  lose  this  quality  when  fre- 
quently repeated.  Acts  the  performance  of 
which  is  at  first  accompanied  by  a  conscious 
effort,  may  by  frequent  repetition  become  largely 
and  in  some  instances  wholly  "automatic,"  i. 
e.,  may  finally  be  unattended  by  consciousness 
either  in  whole  or  in  part.  Many  of  the  acts 
acquired  in  early  life — the  use  of  utensils  in 
eating,  the  adjustments  of  clothing,  the  move- 
ments of  writing,  the  movements  concerned  in 
playing  a  musical  instrument — are  all  acts 
usually  at  first  performed  slowly  and  with  dif- 
ficulty, but  later  with  increasing  ease  until  con- 
sciousness no  longer  enters  into  them.  The  same 
movements  frequently  repeated  necessitate  the 


88  THE  PHYSIOLOGY  OF  MIND 

constant  repetition  of  the  same  association — the 
same  combination — among  the  neurones,  and 
sooner  or  later  the  movements  acquire  all  the 
character  of  fixed  responses. 

The  first  inference  that  is  justified  is  that 
consciousness  disappears  in  proportion  as  fixa- 
tion is  established.  Fixation  of  response  means 
the  disappearance  of  consciousness.  This  in- 
ference leads  to  another  no  less  interesting,  an 
inference  that  follows  as  a  corrollary,  namely, 
that  consciousness  is  present  only  in  the  "ad- 
justable" responses;  that  is,  only  in  those  re- 
sponses which  are  attended  by  a  changing,  an 
actively  varying  relationship  among  the  neu- 
rones. An  impact  transmitted  from  the  cord 
and  segmental  brain  into  the  telencephalon 
brings  about  definite  changes  in  the  synaptic 
relations  of  the  neurones  to  which  the  impact 
is  first  transmitted.  Thence  the  impact  is 
transmitted  to  other  intercalary  neurones,  in- 
deed, to  many  series  of  the  latter  in  the  manner 
already  indicated.  The  transmission  of  the  im- 
pact, subject  to  reinforcement,  may  continue 
until  motor  centers — i.  e.,  until  neurones  in  re- 
lation with  effector  (motor)  neurones  of  the 
segmental  brain  or  cord — are  reached,  when  an 


THE  PHYSIOLOGY  OF  MIND  89 

outward  or  motor  expression  results;  or  the 
transmission  may  continue  to  diffuse  variously 
through  the  cortex  without  a  so-called  motor 
area  being  involved.  Whatever  the  course  of 
the  transmission,  it  is  inevitable  that  the  neu- 
rones concerned  are  involved  in  sequence.  The 
axone- terminals  of  the  first  neurone  approach 
and  are  approached  by  the  dendrites  of  the 
second  (see  p.  71).  The  second  neurone  effects 
a  like  synaptic  approach  with  the  third,  the 
third  with  the  fourth,  and  so  on.  It  follows  that 
just  as  soon  as  an  impact  has  been  transmitted 
by  a  neurone — i.  e.,  just  as  soon  as  it  has  com- 
pleted its  discharge  (see  p.  81) — its  axone  ter- 
minals and  the  dendrites  of  the  receiving  cell 
are  again  retracted,  i.  e.,  the  synaptic  relation- 
ship is  broken  and  the  neurone  is  again  at  rest. 
It  is,  I  believe,  a  legitimate  inference  that  a 
neurone  at  rest  can  have  no  relation  with  con- 
sciousness; a  neurone  at  rest,  so  to  speak,  is  un- 
conscious. It  follows,  therefore,  that  con- 
sciousness is  only  present  in  the  neurones  that 
are  actively  concerned  in  transmission.  Con- 
sciousness is  itself  a  phenomenon  of  cortical 
transmission. 

Let  us  at  this  point  consider  some  of  the  ele- 


90  THE  PHYSIOLOGY  OF  MIND 

mental  facts  of  consciousness  as  they  reveal 
themselves  to  our  individual  experience.  What- 
ever consciousness  may  be,  it  is  something  that 
is  constantly  changing.  A  sensation,  a  percep- 
tion, a  thought  is  experienced.  A  sensation  per- 
sists as  long  as  the  impacts  that  give  rise  to  it 
continue;  a  perception  as  long  as  the  object 
perceived  throws  its  impacts  upon  the  receptors ; 
a  thought  resolves  itself  into  a  train  of  sequences. 
Each  individual  instant  of  time,  however, 
whether  it  is  concerned  in  a  momentary  sensa- 
tion derived  from  a  single  impact  or  whether  the 
sensation  be  made  up  of  many  succeeding  in- 
stants of  impacts,  becomes  past  history  the 
moment  it  is  experienced;  it  immediately  enters 
the  past.  The  same  statement  applies,  of  course, 
to  a  perception,  to  a  thought;  in  fact,  to  any 
mental  process.  While  consciousness  is  con- 
stantly changing  from  the  immediate  present  to 
the  immediate  past,  it  is  of  necessity  also  con- 
stantly passing  into  the  immediate  future. 
Bergson1  expresses  the  same  facts  as  follows: 
"For  consciousness  there  is  no  present,  if  the 
present   be   a   mathematical   instant.     An   in- 

1  Bergson,  Mind  Energy,  transl.  by  H.  Wilson  Carr,  Henry  Holt  & 
Co.,  New  York,  1920,  p.  8. 


THE  PHYSIOLOGY  OF  MIND  91 

stant  is  the  purely  theoretical  limit  which  sepa- 
rates the  past  from  the  future.  It  may,  in  the 
strict  sense,  be  conceived,  it  is  never  perceived. 
When  we  think  we  have  seized  hold  of  it,  it  is 
already  far  away.  What  we  actually  perceive 
is  a  certain  span  of  duration  composed  of  two 
parts — our  immediate  past  and  our  imminent 
future."1 

Surely  these  elemental  facts  are  in  accord 
with  the  principles  governing  transmission 
through  the  cortical  neurones.  This  transmis- 
sion is  a  progressive,  continuous  thing;  receding 
from  the  point  of  entrance  of  the  impact  and  at 
the  same  time  continuously  advancing.  In  con- 
sidering transmission,  however,  it  is  important 
to  bear  in  mind  that  in  addition  to  the  mere 
fact  of  transmission  there  is  the  further  fact  of 
the  release  of  energy  (see  p.  81),  a  release  in 
which  each  neurone  successively  takes  part. 
As  a  result,  an  impact,  thus  continuously  re- 
inforced, becomes  widely  diffused.  This  dif- 
fusion, however,  does  not  take  place  indiffer- 
ently in  all  directions,  but  in  accordance  with 
definite  principles.    To  begin  with,  it  is  obvious 

1  Thus  far  only  is  the  writer  in  accord  with  Bergson's  interpretation 
of  consciousness.    From  this  point  on  Bergson  enters  a  maze  of  mysticism. 


92  THE  PHYSIOLOGY  OF  MIND 

that  transmission  follows  the  direction  of  least 
resistance.  Evidently  the  latter  will  be  in  the 
course*  of  the  most  frequently  travelled  paths, 
those  paths  in  which  the  amoeboid  approach  of 
axone  terminals  and  dendrites  has  been  most 
frequently  established,  or,  to  phrase  it  in  other 
words,  in  which  "synaptic  resistance"  has  been 
most  frequently  overcome.  Further,  it  is  prob- 
able that  the  transmissions,  other  things  equal, 
at  first  followed  the  most  direct  routes  to  the 
gateways  of  exit;  the  demands  for  adjustment 
of  the  responses  to  the  environment  were  in  the 
primitive  mammalian  forms  doubtless  rela- 
tively simple;  as  they  are  to  this  day  in  moles 
and  rabbits,  insectivora,  rodents,  and  the  like. 
However,  the  organism  in  response  to  the  in- 
creasing demands  made  upon  it  by  the  environ- 
ment, reacted  by  increasing  its  power  of  adap- 
tation; it  underwent,  as  we  say,  evolution. 

The  telencephalon  grew,  its  neurones  became 
more  numerous,  and  its  power  of  adjusting  to 
the  environment  the  responses  it  transmitted 
was  correspondingly  increased.  Numerous  "as- 
sociation tracts,"  great  and  small,  gradually 
made  their  appearance,  so  that  every  part  of 
the  cortex  became  connected  with  every  other 


THE  PHYSIOLOGY  OF  MIND  93 

part  (see  p.  61).  Notwithstanding  this  increas- 
ing complexity  and  increased  power  of  adjust- 
ment, notwithstanding  the  great  facility  for  in- 
tercommunication, an  impact  entering  the  tel- 
encephalon is  not  diffused  universally  through- 
out the  entire  cortex.  Doubtless  dependent 
upon  the  nature  of  the  impact — the  exciting 
cause — and  the  special  environment  in  which 
the  organism  happens  to  be  placed,  as  well  as 
upon  other  factors  already  considered  (see  p. 
79),  the  transmission  pursues  a  course  more  or 
less  defined.  The  transmission  is  not,  however, 
entirely  limited  to  this  course,  for  the  neurones 
successively  involved  doubtless  discharge  their 
energy  not  only  into  those  in  the  direct  path- 
way of  the  transmission  but  also  into  neighbor- 
ing neurones  not  directly  concerned.  There  is, 
so  to  speak,  a  lateral  transmission,  but  one  of 
less  dynamic  power,  and  which  finally  dies  out 
within  a  variable  range  of  the  primary  activity. 
Consciousness  follows  the  main  train,  but  also 
includes  a  limited  and  fading  field  to  either  side 
— to  all  sides,  one  might  say.  In  a  sense,  con- 
sciousness is  analogous  to  the  visual  field  with 
its  sharply  defined  central  vision  and  its  grad- 
ually fading  peripheral  areas.    The  "field  of  con- 


94  THE  PHYSIOLOGY  OF  MIND 

sciousness"  becomes  less  and  less  distinct  as  the 
main  train  of  activity — perception,  thought, 
emissive  impulse — is  departed  from.  Gradually 
it  fades  into  the  subliminal,  the  subconscious, 
the  unconscious. 

Again,  the  "train  of  activity"  is  continuous, 
unbroken,  during  the  waking  period.  Further, 
the  inpour  of  impacts  is  incessant,  and  a  given 
"train"  may  be  reinforced,  deflected,  or  modi- 
fied in  various  ways.  Cessation  of  the  "train  of 
activity"  means,  of  course,  cessation  of  the 
synaptic  transmission,  a  discontinuance  of  the 
"amoeboid  approach"  of  axone  terminals  and 
dendrites.  Such  a  discontinuance  means  un- 
consciousness and,  physiologically,  sleep.  In 
one  of  my  papers,1  read  in  1897,  I  expressed 
myself  as  follows:  "Evidently  the  neurones 
when  functionally  active  must  be  in  relation 
with  each  other.  Their  processes  must  be  either 
in  contact  or  nearly  so.  Evidently  this  condi- 
tion is  a  prerequisite  of  consciousness.  Now 
what  happens  when  the  nerve-cells  are  ex- 
hausted by  fatigue,  when  their  volume  and  their 
cell  contents  have  been  diminished,  as  we  have 

1  Dercum,  Application  of  the  Theory  of  the  Movement  of  the  Neuron> 
Univ.  Med.  Magazine,  April,  1897.  See  also  C.  L.  Dana,  J.  A.  M.  A., 
April  24,  1920,  p.  1141. 


THE  PHYSIOLOGY  OF  MIND  95 

every  reason  to  infer  is  the  case,  from  the  ex- 
periments of-  Hodge?  Evidently  their  processes 
become  retracted  and  they  are  no  longer  in  re- 
lation with  each  other.  The  neurone  isolated 
from  the  rest  by  retraction  must  be  without 
function.  General  retraction  of  neurones  must 
mean  absence  of  function,  must  mean  uncon- 
sciousness, must  mean  sleep.  In  other  words, 
in  sleep  the  neurones  have  their  processes  re- 
tracted; in  consciousness  their  processes  are 
extended."1 

Let  us  turn  our  attention  to  some  of  the 
other  considerations  that  present  themselves. 
Evidently  the  extent  of  the  field  of  conscious- 
ness must  depend  upon  the  number  of  neurones 
called  into  activity,  and  this,  in  turn,  must  de- 
pend upon  the  impacts  received,  upon  the 
number,  intensity,  and  character  of  the  latter. 
Further,  it  is  the  summation  of  the  activities  of 
all  the  neurones  aroused  at  a  given  time  which 
constitutes  at  that  time  the  conscious  indi- 
viduality. The  latter  must,  therefore,  be  re- 
garded as  multiple,  as  made  up  of  many  in- 

1  Lugaro's  suggestion  that  during  sleep  there  is  a  general  diffuse 
extension  of  all  nervous  processes  instead  of  a  retraction  would  sub- 
stitute activity  for  rest,  and  is,  so  it  would  appear,  dynamically  incon- 
sistent with  arrest  of  function. 


96  THE  PHYSIOLOGY  OF  MIND 

tegers,  and  of  varying  from  time  to  time  both 
in  extent  and  character.  The  group  activity, 
the  united  activity  of  many  neurones  probably 
gives  rise  to  a  community  of  consciousness,  a 
sense  of  self  as  something  distinct  from  the 
outside  world.  A  discussion  of  the  degree  with 
which  man  shares  this  property  with  other  ani- 
mals would  be  nugatory.  Its  possession,  how- 
ever, by  the  latter  to  any  extent  must  depend 
upon  the  presence  of  'Variable,"  that  is,  "ad- 
justable" responses.  Without  these  a  sense  of 
self  would  obviously  be  impossible.  Further, 
this  "community  of  consciousness"  must  neces- 
sarily vary  in  extent  from  time  to  time  within 
physiological  limits;  that  it  varies  greatly  in 
pathological  conditions  we  will  see  later  on. 

The  community  of  action  of  the  cortical  neu- 
rones must  inevitably  give  rise  to  the  function 
of  memory.  To  make  my  meaning  clear  let  me 
use  the  following  illustration:  A  sequence  of 
sound  vibrations  impinges  upon  the  auditory 
receptors  and  in  due  course  the  impacts  are 
transmitted  to  the  "auditory  center"  in  the 
temporal  lobe  of  the  cerebrum.  Here  the  neu- 
rones assume  relations  with  each  other  corre- 
sponding to  the  impacts  received,  the  character, 


THE  PHYSIOLOGY  OF  MIND  97 

intensity,  and  other  qualities  of  the  latter;  the 
impacts  are  also  transmitted  to  neighboring  and 
possibly  distant  areas.  If  a  similar  series  of 
impacts  has  been  transmitted  by  the  neurones 
before,  similar  or  the  same  combinations  will  be 
re-formed,  and  as  a  corollary  there  will  follow 
a  recognition  by  the  neurones  concerned  in  the 
communal  relation  of  consciousness  as  some- 
thing experienced  before.  That  memory  is  a 
purely  dynamic  function  there  can,  I  think,  be 
no  question.  The  capacity  for  memory  must 
depend  upon"  the  facility  among  the  neurones 
for  re-forming  old  combinations,  and  this  facility 
must  be  increased  by  repetition.  In  a  sense 
memory  is  the  expression  of  the  same  tendency 
to  fixation  of  neurone  combinations  as  has 
given  rise  to  the  fixed  relationships  in  the  palseo- 
encephalon.  Perhaps  some  of  the  "instincts" 
and  "race  memories"  have  their  basis  in  com- 
binations of  such  frequent  recurrence  in  the 
ancestry  that  they  have  acquired  all  the  poten- 
tiality of  inherited  structure. 

One  of  the  most  instructive  phenomena  illus- 
trating the  dynamic  character  of  memory  is 
that  presented  by  memory  temporarily  de- 
layed.   It  is  a  matter  of  common  experience  that 


98  THE  PHYSIOLOGY  OF  MIND 

a  name  which  cannot  at  once  be  recalled  appears 
in  consciousness  after  the  lapse  of  a  fraction  of 
a  second  or,  indeed,  at  times  after  the  lapse  of 
many  seconds,  and  at  a  time  when  the  train  of 
thought  is  already  occupying  another  channel. 
It  would  seem  that  the  impact  leading  to  the 
memory  recall  had  set  in  motion  a  group  of 
neurones  along  paths  only  occasionally  used  or 
long  unused,  or  along  paths  subject  for  the  time 
being  to  synaptic  resistance.  The  significant 
facts  are  that  time  is  required  for  the  act,  and 
that  the  presentation  of  the  name  occurs  auto- 
matically. Another  significant  illustration  of 
the  dynamic  quality  of  memory  is  offered  by 
the  abnormal  memory  occasionally  observed  in 
certain  defective  children,  the  so-called  "idiot 
savants."  The  latter  may  be  able  to  give  cita- 
tions at  great  length  of  matter  which  they  have 
heard  only  once  and  of  the  meaning  of  which 
they  have  no  comprehension;  not  infrequently 
such  citations  are  in  foreign  languages,  of  which 
the  child  is  likewise  ignorant.  Such  abnormal 
memories  suggest  a  pathological  tendency  to 
fixation  of  the  combinations;  perhaps  a  disease 
of  the  synapses.  Further,  it  is  not  improbable 
that  in  these  children  the  tendency  to  fixation 


THE  PHYSIOLOGY  OF  MIND  99 

of  the  cortical  responses  is  directly  related  to 
their  idiocy.  It  would  appear  that  a  certain 
plasticity,  release,  and  freedom  of  combination 
are  essential  to  normal  function. 

Referring  again  to  instincts,  it  is  not  im- 
probable that  some  instincts  are  inherited 
modes  of  reaction  to  the  environment  that  had 
their  origin  in  responses  which  early  in  the 
phylogeny  of  the  race  were  adjustable  and  which, 
owing  to  constant  repetition,  became  fixed  and 
relegated  to  the  subconscious  field.  However, 
other  phenomena  apparently  instinctive  are 
doubtless  due  to  the  mere  physical  reaction  of 
the  organism  to  the  environment  as  pointed 
out  by  Jacques  Loeb.1  In  these  reactions,  like- 
wise, the  responses  being  fixed,  they  play  no 
role,  or  at  most  only  an  indirect  role  in  con- 
sciousness. 

In  our  discussion  of  the  transmission  of  im- 
pacts through  the  telencephalon,  and  especially 
in  our  discussion  of  memory,  we  have  already 
laid  the  foundation  for  the  explanation  of  vari- 
ous detailed  mental  phenomena  such  as  per- 
ception, apperception,  association,  as  expressed 

1  Jacques  Loeb,  Forced  Movements,  Tropisms,  and  Animal  Conduct, 
Lippincott  &  Co.,  Philadelphia,  1918. 


100  THE  PHYSIOLOGY  OF  MIND 

in  the  train  of  thought,  and  the  transmission  of 
the  impact  through  the  avenues  of  exit  to  the 
effectors.  In  the  act  of  perception  the  neurones 
of  the  cortex  which  are  the  recipients  of  a  given 
series  of  impacts  form  combinations  among 
themselves  corresponding  to  the  impacts  re- 
ceived. The  transmission,  of  course,  does  not 
cease  here,  but  continues,  as  already  indicated, 
by  association,  intracortical  and  subcortical, 
many  neurones  being  called  into  activity.  The 
combinations  successively  formed  are  some  of 
them  new,  others  are  combinations  which  are 
the  same  as  or  similar  to  combinations  formed 
upon  previous  occasions.  The  result  is  that  the 
incoming  combinations  resulting  from  the  act 
of  perception  assume  relations  in  part  to  past 
combinations  and.  in  part  to  combinations 
wholly  or  partly  new.  In  other  words,  it  is  the 
function  of  the  common  or  community  con- 
sciousness of  the  neurones  concerned  in  this 
activity  to  collocate  the  impression  received. 
It  is  this  which  constitutes  the  act  of  appercep- 
tion. The  train  of  thought  automatically  fol- 
lows. The  very  act  of  collocation  constitutes 
the  train  of  thought.  It  is  thought,  no  matter 
how  diversified  or  complex  the  transmission  may 


THE   PHYSIOLOGY  OF  MIND  101 

become.  If  it  finally  eventuates  in  a  discharge 
through  an  emissive  gateway,  its  further  prog- 
ress to  the  effectors  is,  of  course,  outside  the 
field  of  consciousness. 

It  is  evident,  let  us  resume,  that  the  neurones 
of  the  telencephalon  are  roused  into  action  by 
the  impacts  transmitted  to  them  from  the  seg- 
mental brain.  As  a  result,  the  neurones  in- 
volved in  a  given  transmission  extend  their 
processes  and  enter  into  synaptic  relations  with 
other  neurones,  into  which  they  also  discharge. 
It  is  the  active  neurones  alone,  as  already 
pointed  out,  which  are  concerned  in  conscious- 
ness. Those  which  are  quiescent  are  those  into 
which  transmission  has  not  taken  place,  and 
consequently  cannot  manifest  consciousness.  In 
contrast  with  the  field  of  consciousness,  they 
therefore  occupy  the  unconscious  field.  It  is 
further  evident  that  in  the  progress  of  a  trans- 
mission through  the  cortex,  neurones  previously 
quiescent  and  therefore  in  the  unconscious  field 
are  brought  into  action  and  now  become  part  of 
the  conscious  field,  and  at  the  same  time  other 
neurones  through  which  transmission  has  been 
completed  again  become  quiescent  and  lapse 
into  the  unconscious  field.    In  other  words,  the 


102  THE  PHYSIOLOGY  OF  MIND 

conscious  and  unconscious  fields  are  constantly 
changing;  that  which  at  one  moment  is  con- 
scious field  at  the  next  moment  is  unconscious 
field,  and  vice  versa. 

Again,  when  a  transmission  passes  through  a 
group  of  neurones,  the  latter  react  by  forming 
combinations  among  themselves  corresponding 
to  the  impacts  received  (see  p.  76).  A  repeti- 
tion of  the  same  or  similar  impacts  means  the 
re-formation  of  the  same  or  similar  combina- 
tions (see  p.  80).  This  implies  the  establish- 
ment of  pathways  of  least  resistance,  and  it 
would  seem  that  a  single  transmission  of  an 
impact  is  sufficient  to  establish  such  a  path- 
way. In  other  words,  the  passage  of  transmis- 
sions establishes  "associations"  among  the  neu- 
rones. These  are  manifest  only  when  the  neu- 
rones are  active,  and  are  merely  potential  when 
the  neurones  are  quiescent.  It  would  appear 
that  when  the  latter  are  stimulated  by  a  trans- 
mission, previous  combinations  are  automat- 
ically reproduced.  In  this  lies,  I  believe,  the 
explanation  of  the  physiology  of  the  uncon- 
scious field.1    The  latter  is  a  vast  storehouse  of 

1 1  do  not  like  the  expression  "unconscious  mind";  the  words  are 
self-contradictory. 


THE  PHYSIOLOGY  OF  MIND  103 

past  experiences.  These  are  represented  not  by 
gross  changes  of  structure,  but  merely  by  po- 
tential possibilities.  Whether  certain  combina- 
tions— associations — are  re-formed  depends  en- 
tirely upon  whether  the  neurones  concerned  are 
reached  by  a  given  transmission. 

Further,  it  is,  I  believe,  a  legitimate  inference 
that  the  number  of  neurones  in  action  at  a 
given  time  is  an  exceedingly  small  part  of  the 
sum  total  of  the  neurones  of  the  cortex.  It  is 
very  probable  that  the  number  concerned  in  the 
field  of  consciousness — in  the  train  of  trans- 
mission, in  the  train  of  thought — is  relatively 
insignificant  when  compared  with  the  ten  thou- 
sand millions  of  the  total.  Finally,  when  we 
consider  the  number  and  complexity  of  both 
the  axone  terminals  and  of  the  dendrites,  and 
the  fact  that  every  part  of  the  cortex  is  in  rela- 
tion with  every  other  part,  we  can  perhaps  form 
a  faint  conception  of  the  practically  limitless 
possibilities  of  association.  Not  only  may  the 
latter  consist  of  combinations  representing  im- 
pacts the  same  as  or  similar  to  impacts  already 
transmitted  but  also  of  combinations  entirely 
new.  The  organism  is  constantly  exposed  to 
new  and  changing  relations  to  the  environment, 


104  THE  PHYSIOLOGY  OF   MIND 

and  to  these  demands  the  organism  reacts  by  a 
constant  readjustment  in  its  responses.  The 
individual  from  infancy  on,  from  his  very  ear- 
liest experiences,  throughout  his  training  and 
education,  up  to  the  complex  experiences  of 
adult  life,  is  constantly  making  fresh  adjust- 
ments, i.  e.,  new  combinations,  new  associations 
among  his  neurones. 

There  can  be  no  doubt  that  the  power  of  the 
continued  making  of  new  combinations  differs 
in  individuals.  In  the  larger  number  the  com- 
binations that  are  formed  resemble  those  that 
are  formed  by  other  individuals  under  the  same 
circumstances,  i.  e.,  who  are  exposed  to  the 
same  impacts.  In  others,  a  relatively  small 
number,  the  combinations  differ  in  a  degree 
sometimes  slightly,  sometimes  widely,  from 
those  formed  by  the  average  individual.  It  is 
the  novel  character  of  the  associations  formed 
among  the  neurones  that  constitutes  "origin- 
ality." If  the  novelty  of  the  association  be  very 
pronounced,  it  gives  rise  to  "imagination"; 
originality  and  imagination  are  close  kin. 

The  field  of  consciousness — i.  e.,  the  train  of 
transmission — is,  of  course,  of  relatively  greater 
dynamic  power  than  the  unconscious  field  into 


THE   PHYSIOLOGY  OF  MIND  105 

the  neurones  of  which  it  successively  discharges. 
Whether  into  the  field  of  activity  itself  fresh 
impacts,  impacts  derived  from  other  sources 
than  that  which  originally  gave  rise  to  the 
transmission,  find  entrance,  is  purely  a  question 
of  dynamics.  If  the  dynamic  level  of  the  active 
field  be  relatively  high,  the  ingress  of  disturbing 
impacts  is  excluded  and  the  original  transmis- 
sion pursues  its  way  undisturbed  and  untram- 
meled.  In  such  case  it  is  open  only  to  impacts 
derived  from  the  same  source  that  gave  rise  to 
it  and  which  continually  reinforce  it.  It  is  this 
which  constitutes  "attention."  Lack  of  atten- 
tion, the  inability  for  sustained  attention,  is  due 
to  the  ingress  of  interfering  transmissions  and, 
other  things  equal,  is  expressive  of  a  lower  dy- 
namic level — i.  e.,  of  weakness. 

Similarly,  the  relatively  high  dynamic  level 
of  the  conscious  field  especially  when  joined 
with  novel  associations  gives  rise  to  "initiative," 
to  the  outward  expression,  to  the  discharge — 
through  the  emissive  gateways — of  the  cortical 
energy.  Between  "initiative"  and  "will"  or 
"will  power"  there  is  again  a  close  kinship. 
Given  the  exclusion  of  interfering  transmissions 
as  in  attention,  or  in  that  higher  degree  of  at- 


106  THE  PHYSIOLOGY  OF  MIND 

tention  to  which  we  apply  the  term  "concen- 
tration," and  given  a  high  dynamic  level  of  the 
train  of  transmission — the  field  of  conscious- 
ness— "will  power"  is  the  necessary  outcome. 
The  dynamic  level  of  the  field  of  consciousness 
— i.  e.y  the  output  of  energy — must  inevitably 
depend  upon  the  intensity  of  the  metabolic 
processes,  the  chemical  changes,  going  on  in  the 
substance  of  the  neurones  and  upon  the  number 
of  the  neurones  taking  part. 

To  the  conception  of  the  purely  automatic 
character  of  the  phenomena  of  transmission,  of 
the  amoeboid  movements  and  the  serial  dis- 
charges— in  short,  of  the  physico-chemical 
changes  which  constitute  the  train  of  conscious- 
ness, we  must  now  add  another,  or  rather  re- 
call to  our  minds  a  quality  of  the  neurone  al- 
ready in  part  considered.  Consciousness  im- 
plies "sentiency"  (see  p.  84)  as  a  property  of 
the  neurone.  Consciousness  without  this  prop- 
erty would  cease  to  be  consciousness.  Sensa- 
tion is  a  self-evident  condition  of  consciousness 
and  is  inseparable  from  it.  Now  we  have  al- 
ready considered  some  of  the  fundamental  reac- 
tions of  living  protoplasm  to  the  incident  forces 
of  the  environment,  the  gradual  evolution  of 


THE  PHYSIOLOGY  OF  MIND  107 

special  receptors,  and  the  evolution  of  special 
portions  of  the  primitive  brain,  the  "segmental 
brain,"  into  which  the  impacts  are  transmitted. 
These  are  differentiated  in  the  fish  into  an 
"olfactory  brain,"  an  "eye  brain,"  an  "ear 
brain,"  a  "skin  brain"  (see  p.  50).  The  infer- 
ence becomes  unavoidable  that  these  structures 
respectively  experience  the  sensations  of  odor, 
light,  sound,  and  touch  (see  p.  84).  The  ques- 
tion now  arises  what  role  does  the  telencephalon, 
the  great  usurper,  play  in  this  respect.  From 
the  evidence  of  structure,  only  one  inference  is 
possible,  namely,  that  the  impacts  from  the 
various  receptors  are  transmitted  to  the  cortex. 
If  transmitted  to  the  cortex  they  must  be  still 
farther  transmitted,  diffused,  according  to  the 
principles  indicated  in  the  preceding  pages.  We 
have  no  reason  to  infer  that  the  mode  of  motion 
of  the  impact  is  thereby  changed,  i.  e.,  in  pass- 
ing from  the  neurones  of  the  segmental  brain 
to  those  of  the  telencephalon  or  in  the  passage 
from  the  gateway  of  ingress  to  other  areas  of 
the  cortex;  and,  if  this  be  true,  it  can  only  be 
that  sound,  for  instance,  is  experienced  in  every 
neurone  reached  by  the  transmission;  or  light, 
or  smell,  or  touch,  as  the  case  may  be.    When, 


108  THE  PHYSIOLOGY  OF  MIND 

as  is  frequently  the  case,  transmissions  are  re- 
ceived simultaneously  from  several  special  sense 
receptors,  the  impacts  do  not  interfere  with  each 
other.  Both  the  sound  and  the  object  that 
produces  it  may  be  perceived  at  the  same  time; 
one  through  the  receptors,  for  hearing  and  the 
other  through  the  receptors  for  vision.  Cor- 
responding neurone  associations,  as  already  in- 
dicated, are  formed.  So  it  is  doubtless  when 
the  impacts  are  received  from  many  receptors; 
for  instance,  of  sound,  sight,  smell,  taste,  touch, 
all  at  the  same  time.  This  would  seem  to  be  a 
necessary  result  of  the  elemental  reactions  of 
protoplasm  to  the  incident  forces  of  the  en- 
vironment; a  matter  which  we  have  already 
fully  discussed  (see  p.  33  et  seq.). 

It  would  appear  to  be  a  logical  conclusion 
that,  in  a  sense,  the  entire  cortex  sees,  hears, 
smells,  tastes,  and  feels  wherever  it  is  traversed 
by  the  transmission.  The  so-called  cortical 
centers  appear  merely  to  be  avenues  of  ingress 
and  egress  to  the  general  cortex,  as  already 
pointed  out.  To  be  sure,  the  cortex  varies  in 
its  different  parts  in  its  detailed  structure  and 
presents  peculiarities  in  both  the  receptive  and 
emissive  areas;  e.  g.,  in  the  'Visual  area"  in  the 


THE  PHYSIOLOGY  OF  MIND  109 

occipital  lobe  and  in  the  centers  of  the  "motor 
area."  Here  peculiarities  of  structure  are  found 
whose  function  is  that  apparently  of  the  rein- 
forcement of  transmissions.  However,  the  neu- 
rone of  the  telencephalon  appears  to  have  re- 
tained along  with  its  lack  of  fixation,  along  with 
its  amoeboid  movement,  the  general  elemental 
qualities  inherent  in  the  primitive  neuroblast, 
elemental  qualities  which  are  shared  by  the  en- 
tire cortex.  Other  things  equal,  this  lack  of 
fixation  of  function,  like  the  absence  of  fixation 
of  the  neurone  itself,  appears  to  have  been  and 
still  is  a  necessary  condition  of  its  continued 
evolution.  Differentiation  and  specialization, 
therefore,  while  it  has  taken  place  in  the  cortex, 
has  not  interfered  with  the  continued  adapta- 
tion and  adjustment  of  responses  and  the  con- 
tinued forming  of  new  associations  or  combina- 
tions. Sensations  are  only  experienced  by  the 
neurones  taking  part  in  the  transmission,  and 
these  sensations  doubtless  depend  for  their  kind 
upon  the  special  receptors  by  which  the  im- 
pacts are  received.  The  kinds  of  impact  are 
much  more  numerous  than  would  be  implied  by 
a  consideration  merely  of  the  senses  of  smell, 
taste,  vision,  hearing,  and  touch.     There  are, 


110  THE   PHYSIOLOGY  OF  MIND 

first,  the  subdivisions  of  vision;  namely,  the  per- 
ception of  moving  objects,  of  form,  and  color; 
secondly,  the  addition  to  the  receptors  for 
hearing  of  those  for  equilibrium  and  sense  of 
position,  and,  lastly,  the  addition  to  touch  of 
the  senses  of  pressure,  temperature,  and  pain. 

In  addition  to  the  receptors  which  receive  im- 
pacts from  sources  external  to  the  body,  there 
are  receptors  which  receive  impacts  arising 
within  the  body.  Sherrington,  as  already  stated, 
has  termed  the  first  "exteroceptors"  and  the 
second  "interoceptors."  Besides  these  there  is 
a  third  group  of  receptors  situated  in  muscles, 
bones,  and  joints,  which  give  information  as  to 
the  state  of  these  structures  when  the  parts 
concerned  are  moved.  These  Sherrington  has 
termed  "proprioceptors." 

It  is  quite  clear,  let  us  repeat,  that  the  specific 
sensations  aroused  are  dependent  upon  specific 
impacts  received.  In  addition  to  these,  how- 
ever, the  neurone  when  active — i.  e.,  when  tak- 
ing part  in  the  train  of  consciousness — also  ex- 
periences other  sensations,  namely,  those  com- 
prised by  pleasure,  pain,  the  emotions  or  af- 
fects. These  may  be  slight,  moderate,  or  in- 
tense in  degree.     In  their  production  the  in- 


THE  PHYSIOLOGY  OF  MIND  111 

ternal  secretions,  the  hormones,  and  the  sym- 
pathetic and  autonomic  nervous  systems  play  an 
important  role;  at  times  the  active  cause  is  to  be 
sought  in  toxic  substances  bred  within  the  body 
or  taken  in  from  without.  There  is  every  rea- 
son to  believe  that  the  impacts  which  give  rise 
to  sensations  of  pleasure  and  pain  affect  primar- 
ily neurones  in  the  segmental  brain,  the  palaeo- 
encephalon,  namely,  "cortical  dependencies" 
in  the  thalamus  (see  p.  58).  That  they  are 
transmitted  to  the  telencephalon  and  that 
they  play  a  role  in  consciousness  and  pro- 
foundly influence  the  train  of  neurone  activity 
in  the  cortex  goes  without  saying.  The  hor- 
mones or  toxins  probably  act  upon  the  sympa- 
thetic nervous  system,  upon  the  neurones  of 
the  thalamus,  and  the  neurones  of  the  cortex; 
it  is  probable  that  in  the  latter,  in  many  in- 
stances, they  act  upon  the  synapses.  If  this  be 
the  case,  transmission  must  be  profoundly  in- 
fluenced. On  the  one  hand,  it  may  be  greatly 
retarded  or  inhibited,  as  in  depressed  mental 
states,  e.  g.,  in  melancholia,  in  which  we  have 
probably  to  do  with  a  toxic  hormone  as  the 
cause  both  of  the  mental  pain  and  the  retarda- 
tion of  the  mental  processes.     How  much  the 


112  THE  PHYSIOLOGY  OF  MIND 

retardation  of  itself  may  serve  as  a  cause  of 
mental  pain  is  an  interesting  question;  probably 
it  also  plays  a  role.  Interference  with  the  syn- 
apses doubtless  retards  the  "discharge  of  en- 
ergy" to  the  neurones  next  in  succession,  and 
this  "blocking"  or  retardation  of  function  may 
itself  be  a  cause  of  pain  in  the  neurone. 

In  the  opposite  condition,  that  of  mania,  the 
normal  resistance  offered  by  the  synapses  is 
greatly  lessened;  there  is  a  general  release  of 
inhibition  and  it  is  not  improbable  that  the  re- 
sulting increase  of  discharge,  the  heightening  of 
function,  is  directly  related  to  the  "expansion," 
the  pleasurable,  aggressive,  mental  attitude  so 
characteristic  of  this  condition. 

Speculation  as  to  the  details  possible  or  prob- 
able in  the  play  of  the  emotions  may  lead  us 
astray,  but  perhaps  a  few  thoughts  as  to  some 
of  the  fundamental  physical  principles  which 
may  underlie  such  elementary  phenomena  as 
pleasure  and  pain  may  not  be  amiss.  For  ex- 
ample, certain  sequences  and  certain  combina- 
tions of  sound  give  us  the  pleasurable  sensa- 
tion which  we  term  "music."  The  thought 
suggests  itself  that  the  impacts  transmitted  to 
the  neurones,  i.  e.,  the  vibrations,  are  of  such  a 


THE  PHYSIOLOGY  OF  MIND  113 

character  as  to  be  taken  up  by  the  molecules  of 
the  neurones  without  causing  a  disruption  of 
their  structure,  or  at  most,  only  a  minimal  con- 
sumption of  substance.  It  is  probable  that 
sounds  which  are  harsh,  discordant,  cacapho- 
nous,  are  painful  because  they  actually  cause 
destruction  of  the  neurone  molecule.  Con- 
sumption of  substance  accompanies  all  dis- 
charge of  function  (see  p.  81),  but  impacts 
that  result  in  motions  that  are  possible  to  or 
in  harmony  with  the  structure  of  the  neurone 
molecule  are  probably  accompanied  by  pleasur- 
able sensations.  Possibly  in  some  such  thought 
as  this  is  to  be  found  the  explanation  of  the 
pleasure  and  pain  experienced  through  the 
other  senses.  May  we  perhaps  be  permitted 
to  extend  this  conception  to  pleasurable  and 
painful  emotions?  How  markedly  the  latter 
are  at  times  attended  by  the  evidences  of 
physical  exhaustion — i.  e.t  consumption  of  sub- 
stance— need  hardly  be  pointed  out.  The 
relation  between  general  nutrition  and  a  sense 
of  well-being  is  well  known.  Many  factors, 
however,  enter  into  the  problem,  and  a  detailed 
consideration  of  the  affective  qualities  of  mind 
would  lead  us  too  far  afield.     Suffice  it  to  say 


114  THE  PHYSIOLOGY  OF  MIND 

that  the  elemental  qualities  of  pain  and  pleasure 
were  in  primitive  forms  doubtless  related,  on 
the  one  hand,  to  injurious  or  destructive  influ- 
ences, and,  on  the  other,  to  the  intake  of  food 
and  other  physical  compliance  with  the  needs 
of  the  organism.  Later,  in  the  course  of  evolu- 
tion, there  ensued  specializations  and  differen- 
tiations of  impressions,  impressions  derived 
both  from  the  external  world  and  from  the 
body  of  the  organism  itself.  At  the  same  time 
special  receptors,  both  extero-  and  intero- 
ceptors,  together  with  special  neurone  path- 
ways were  evolved.  Later,  with  the  increasing 
development  of  the  telencephalon,  there  came 
a  further  differentiation  in  the  impressions  and 
their  corresponding  neurone  reactions  and  an 
increase  in  the  adjustment  of  the  response, 
i.  e.,  in  the  behavior  of  the  individual.  Into 
the  final  result  there  may  have  entered,  on 
the  one  hand,  physical  pain  or  physical  pleasure; 
or  on  the  other,  joy,  satisfaction,  sorrow,  dis- 
appointment; or,  it  may  be,  a  refined  feeling  of 
altruism  or  perhaps  of  an  almost  impersonal 
regret. 

In   the  preceding  pages   the   writer  has   en- 
deavored to  apply  purely  physical  conceptions 


THE   PHYSIOLOGY  OF  MIND  115 

to  the  interpretation  of  mind.  The  view  that 
mental  phenomena  are  in  their  essence  physical 
finds  confirmation  in  the  facts  of  so-called 
psychophysics.  These  embrace  especially  the 
results  of  the  experimental  study  of  the  time 
relations  of  mental  processes  and  of  the  phe- 
nomena underlying  the  sense  impressions. 
While  a  consideration  of  these  phenomena 
in  detail  would  here  be  out  of  place,  let  it 
suffice  to  say  that  as  regards  the  first,  namely, 
the  time  relations  or  reactions — the  time  re- 
quired for  the  response  to  sense  impressions — 
they  are  significant  in  the  fact,  first,  that  any  time 
at  all  is  required,  and  secondly,  that  this  time 
is  in  distinct  relation  to  the  complexity  of  the 
experiment  and  the  condition  of  the  individual; 
i.  e.,  whether  the  latter  be  in  good  health, 
whether  he  be  fatigued,  or  perhaps  under  the 
influence  of  some  stimulant  or  drug,  or  the 
subject  of  disease.  Clearly,  all  these  factors 
are  physical  in  their  nature.  In  this  connec- 
tion the  interesting  facts  of  the  "personal 
equation"  in  the  making  of  astronomical  and 
other  scientific  time  observations  also  present 
themselves.  We  are  forcibly  reminded,  too, 
of   the   part   which   the   synapses   play   in   the 


116  THE  PHYSIOLOGY  OF  MIND 

delay  of  responses;  though  it  goes  without 
saying  that  some  time  must  necessarily  also 
be  consumed  in  the  transmission  through  the 
dendrites,  bodies,  and  axones  of  the  neurones. 

It  is,  however,  in  the  field  of  the  experimental 
studies  upon  sense  impressions  that  the  most 
significant  and  most  convincing  results  have 
been  achieved.  It  was  found,  for  instance, 
that  a  sensation  aroused  by  a  given  impres- 
sion •  having  been  noted,  an  increase  in  that 
sensation  can  only  be  brought  about  by  a 
proportionate  increase  in  the  intensity  of  the 
impression.  It  was  found,  further,  that  in 
order  to  bring  about  such  an  increase  of  sensa- 
tion, the  increase  of  intensity  of  the  impres- 
sion made  upon  the  receptors  must  be  in  a 
geometric  ratio  to  the  increase  of  sensations; 
that  is,  the  intensity  of  the  sensation  increases 
in  an  arithmetic  progression,  the  intensity  of 
the  stimulus  in  a  geometric  proportion.  Thus, 
a  man  capable  of  distinguishing  between  the 
weight  of  16  ounces  and  17  ounces,  cannot 
distinguish  between  32  and  33  ounces,  but 
only  between  32  and  34  ounces.  Again,  a 
man  capable  of  distinguishing  between  20  and 
21  grammes,  testing  a  weight  of  250  grammes 


THE  PHYSIOLOGY  OF  MIND  117 

cannot  tell  when  an  increase  is  reached  until 
12.5  grammes  are  added.  If  he  looks  at  a 
light  of  10  candle-power  he  cannot  become 
conscious  of  an  increase  in  the  intensity  of  the 
light  until  2  candle-power  are  added;  if  he  looks 
at  a  60  candle-power  flame  12  candle-power 
must  be  added;  if  it  is  a  2000  candle-power 
light,  400  candle-power  must  be  added.1  Similar 
facts  obtain  as  regards  the  appreciation  of 
intensity  of  sounds  and  as  regards  intensities 
of  pressure.  As  regards  the  senses  of  taste 
and  smell,  of  temperature,  and  the  various 
somatic  and  visceral  sensations,  the  conditions 
are  such  as  to  preclude  very  satisfactory  experi- 
mentation. However,  in  regard  to  the  senses 
in  which  such  studies  are  possible,  there  can 
be  no  doubt  as  to  the  facts.  A  physiologist  of 
a  past  generation,  Weber  of  Leipzig,  discovered 
these  facts  more  especially  in  regard  to  auditory 
and  cutaneous  sensations,  and  they  constitute 
what  is  today  known  as  Weber's  law.  Many 
studies  have  since  been  made  and  various 
interpretations  advanced,  e.  g.,  by  Wundt  and 
by  Fachner,  and  the  facts  may  be  briefly  sum- 
marized as  follows:  an    increase    of    sensation 

1  Ebbinghaus,  Abriss  der  Psychologie,  1909,  pp.  66,  67. 


118  THE  PHYSIOLOGY  OF  MIND 

depends,  as  above  stated,  upon  a  proportionate 
increase  of  the  stimulus;  the  increase  of  sensa- 
tion is  in  arithmetic  progression,  that  of  the 
stimulus  in  geometric  progression;  or,  to  state 
it  in  other  words,  the  sensation  increases  in 
proportion  to  the  logarithm  of  the  stimulus. 

Clearly  we  have  here  a  hint  not  as  to  the 
relations  between  physical  impressions  and  a 
spiritual  world,  as  various  interpretations  would 
lead  us  to  believe,  but  a  hint  as  to  the  structure 
of  the  proteins  that  make  up  the  neurone  and 
the  physical  laws  which  these  proteins  must 
obey.  In  a  sense  Weber's  law  is  as  purely 
physical  as  the  one  which  tells  us  that  light  is 
inversely  as  the  square  of  the  distance  and 
must  be  equally  accepted.  The  facts  of  Weber's 
law,  however,  lead — it  seems  .to  the  writer — 
to  inferences  far  more  fundamental  and  im- 
portant. We  have  already  seen  that  the  num- 
ber and  character  of  the  impacts  which  living 
protoplasm  can  take  up  is  comparatively  small. 
Only  in  an  extremely  limited  degree  do  the 
changes  induced  in  the  protoplasm  represent 
the  changes — the  multiplicity  of  forces — in  the 
outside  world.  To  this  conception  Weber's 
law  adds  another;  namely,  that    such  changes 


THE  PHYSIOLOGY  OF  MIND  119 

as  are  represented  are  only  approximate;  the 
very  constitution  of  the  protein  molecules  for- 
bids an  even  and  continuous  recognition  of  the 
increasing  intensity  of  impacts.  If  this  is  true 
of  the  recognition  of  so  simple  a  quality  as  in- 
crease of  intensity,  may  it  not  be  true  also  of 
other  qualities  of  the  impacts?  The  thought 
that  suggests  itself  is  that  the  changes  induced 
in  living  protoplasm  by  the  impacts  are,  first, 
only  such  as  the  protoplasm  is  capable  of  receiv- 
ing and,  secondly,  that  these  may  and  probably 
do  in  themselves  correspond  only  imperfectly 
to  the  changes  going  on  in  the  outside  world. 
We  can  only  be  conscious  of  the  changes  in  the 
protoplasm  of  our  own  substance,  i.  e.,  the 
changes  in  the  proteins  of  our  neurones;  our 
knowledge  of  the  outside  world  is  necessarily 
limited  to  these  changes  and  must  of  necessity 
be  imperfect.  Further,  our  knowledge  is  purely 
inferential.  That  multiple  qualities  of  the  out- 
side world  produce  no  changes  in  the  proteins 
of  the  neurones  we  have  already  seen;  that 
other  qualities  induce  changes  which  only  im- 
perfectly represent  those  of  the  outside  world 
is,  it  must  be  conceded,  equally  true.  What 
are  we  to  say  of  the  memory  pictures  and  of 


120  THE  PHYSIOLOGY  OF  MIND 

the  general  and  abstract  conceptions  based 
upon  these?  Of  the  memory  pictures  it  may 
be  said  that  they  can  at  best  represent  only 
more  or  less  approximately  actual  past  re- 
sponses to  impacts.  Of  the  general  concep- 
tions^— i.  e.,  the  composite  pictures  resulting 
from  accumulated  responses — it  may  be  said 
that  they  are  at  best  imperfect  approximations 
to  general  external  truths,  and  are  liable  to 
vary  and  change  with  additions  to  the  impacts 
and  corresponding  fresh  responses;  that  is, 
with  an  increasing  experience.  When  we 
approach  the  field  of  abstract  conceptions  we 
clearly  tread  upon  dubious  ground.  In  reality, 
abstract  conceptions  represent  nothing  that 
actually  exists  in  the  outside  world.  At  most 
they  are  artificial  pegs  upon  which  to  hang 
the  logic  of  our  ideas.  And,  as  regards  our 
logic,  is  not  this  faculty  dependent  upon  our 
own  structure,  upon  the  arrangement  of  our 
neurones,  and  upon  their  contained  proteins 
and  other  substances?  In  how  far  is  it  to  be 
trusted?  Does  it  not  at  times  lead  us  into 
gross  absurdities?  We  need  but  recall  the  time- 
worn  story  of  the  race  between  the  hare  and 
the  tortoise.     Each  interval  of  space  existing 


THE  PHYSIOLOGY  OF  MIND  121 

between  the  two  is  divisible,  and  no  matter 
how  small  the  space  may  become  it  is  still 
divisible;  indeed,  it  is  inconceivable  that  the 
space  should  become  so  small  that  it  should 
not  be  still  further  divisible;  and  so  it  becomes 
logically  impossible  for  the  hare  ever  to  catch 
the  tortoise.  Similar  vagaries  of  neurone  activity 
doubtless  lie  at  the  basis  of  such  abstractions 
as  the  fourth,  fifth,  and  sixth  dimensions  of 
space.  As  regards  the  fourth  dimension,  Ein- 
stein, after  pointing  out  the  relations  of  a  given 
body  to  the  three  dimensions  of  space,  points 
out  that  all  bodies  in  the  universe  are  in  motion, 
and  as  it  takes  time  for  a  given  body  to  move 
from  one  point  to  another,  time  is  the  fourth 
"dimension"  of  space.  To  my  way  of  think- 
ing, it  would  be  better  to  say  that  time  is  an 
essential  factor  in  all  conceptions  of  spatial 
relations1;  or  to  put  the  fact  into  simpler  lan- 
guage, merely  to  say  that  "all  space  is  filled 
with  moving  matter."  Time  and  the  three 
dimensions  of  space  are  abstract  conceptions, 
but  the  conception  of  "dimensions"  having 
once  been  admitted,  it  becomes  logically  cap- 

1  In  a  sense,  every  measurable  element  is  a  dimension,  and  in  this 
sense  time  is  a  fourth  dimension  of  space. 


122  THE  PHYSIOLOGY  OF  MIND 

able  of  indefinite  multiplication;  hence  the 
fifth,  sixth,  and  further  dimensions  of  space. 
Is  there  not  here  an  analogy  to  the  logic  of  the 
race  between  the  hare  and  the  tortoise?  In 
one  instance  there  is  indefinite  division,  in  the 
other,  indefinite  multiplication. 

Evidently  the  logical  process  must  be  con- 
stantly curbed,  held  in  check,  inhibited  by 
the  correcting  influence  of  the  impressions 
received  from  the  external  world.  We  know 
that  the  hare  does  pass  the  tortoise,  and  we 
know  also,  no  matter  what  our  mathematical 
friends  may  say,  that  the  multiplication  of  the 
"dimensions"  is  in  crass  contradiction  with  the 
orientation  of  our  senses,  i.  e.,  with  human 
experience. 


A  biological  interpretation  of  mind  leads,  I 
believe,  to  a  more  wholesome,  a  saner  concep- 
tion of  its  functions  and  limitations.  It  may 
be  noted  that  in  this  essay,  up  to  the  present 
moment,  the  word  "psyche"  or  its  equivalents 
and  derivatives  have  not  been  employed.  At 
the  very  outset  the  necessity  was  pointed  out 
of  laying  aside  preconceived  ideas,  prejudices, 


THE  PHYSIOLOGY  OF   MIND  123 

and  beliefs.  To  introduce  at  this  point  an 
"immaterial"  something,  of  unknown  and  un- 
ascertainable  character,  to  insert  such  a  some- 
thing into  the  problem  renders  the  latter 
hopelessly  unintelligible.  Further,  when  we 
pause  to  consider  the  intrinsic  meaning  of  the 
word  psyche  and  its  equivalents,  most  sugges- 
tive inferences  present  themselves.  The  Greek 
word  "fyvxyi  has  the  primitive  meaning  of  the 
breath;  indeed,  given  the  Greek  pronunciation, 
the  sound  is  literally  that  of  the  escaping 
breath.  In  primitive  times  the  "breath"  was 
looked  upon  as  the  vital  principle,  and  its 
final  escape  in  the  act  of  dying  as  the  departure 
of  that  vital  principle.  The  ^vyy]  naturally 
and  subconsciously  represented  the  idea  of  an 
"immaterial"  constituent  of  our  beings.  A 
similar  interpretation  is  applicable  to  the  Latin 
word  spiritus,  the  primitive  meaning  of  which 
is  likewise  air,  exhalation,  breath,  and  its  root 
still  forms  the  integral  parts  of  the  words 
respiration,  inspiration,  expiration.  The  Latin 
word  "mens"  is  free  from  such  objections, 
for  it  literally  means  the  mind,  the  under- 
standing, the  intellect,  and  to  me  it  has 
seemed  much   more  fitting   to   employ   its   de- 


U±  THE  PHYSIOLOGY  OF  MIND 

rivatives  than  those  derived  from  -^v^  or  from 
spiritus. 

In  conclusion,  I  may  perhaps  be  permitted 
to  say  that  there  is  nothing  in  the  position  here 
assumed  which  should  shock  or  give  pain  to 
any  one.  The  study  of  the  recondite  problems 
of  human  existence  is  in  a  sense  a  study  that 
is  imperative  and  should  be  pushed  to  its  ulti- 
mate conclusions.  Our  knowledge  of  the.  con- 
stitution of  the  universe  as  revealed  by  the 
marvelous  truths  of  radio-activity,  of  the  struc- 
ture of  the  atom,  and  by  the  field  opened  up 
by  Einstein's  discoveries  and  theories,  is  but 
an  expression  of  this  tendency;  surely  it  should 
not  be  denied  us  in  the  study  of  mind.  The 
modern  study  of  the  atom  reveals  it  to 
be  but  an  expression  of  energy,  indestruct- 
ible, persistent,  unknowable.  Does  not  this 
cause  the  difference  between  the  old  con- 
ceptions of  ''material"  and  "immaterial"  to 
disappear?  Does  it  not  make  unnecessary — 
as  it  is  impossible — a  "dual"  conception  of 
the  universe?  Finally,  we  should  remember, 
that  as  regards  religious  conceptions,  each 
human  being  is  entitled  to  hold  such  faith  as  he 
chooses,  and,  further,  that  it  is  the  necessary 


THE  PHYSIOLOGY  OF  MIND  125 

and  essential  attribute  of  religious  faith  that  it 
should  be  incapable  of  scientific  proof.  A  relig- 
ious faith  that  would  be  capable  of  mathemat- 
ical demonstration  would  be  no  faith  at  all. 


ADDENDUM    ON   THE    PATHOLOGICAL 
PHYSIOLOGY  OF  MIND 

An  application  of  the  facts  and  deductions 
embraced  by  the  within  essay  to  mental  disease 
is  both  obvious  and  interesting,  and  the  writer 
has  thought  it  fit  to  add  the  following  para- 
graphs. 

In  the  body  of  the  essay,  the  writer  has 
pointed  out  how  the  retraction  of  the  dendrites 
and  axones  of  the  neurones  explains  the  palsies 
and  anaesthesias  of  hysteria.  In  other  words, 
the  functional  break  is  referred  to  the  synapses. 
A  similar  explanation  applies  to  the  palsies 
and  anaesthesias  of  hypnosis  which,  as  Gilles 
de  la  Tourette  long  ago  pointed  out,  is  merely 
hysteria  artificially  evoked.  All  of  the  phe- 
nomena of  these  states  are  undeniably  mental, 
i.  e.y  cortical  in  their  origin.  This  is  true  alike 
of  the  motor,  sensory,  visceral,  as  well  as  the 
more  strictly  mental  reactions.  In  hypnosis, 
for  instance,  a  partial  sleep  is  induced  in  which 
the    admission    of    impacts    from    the    various 

126 


THE   PHYSIOLOGY  OF  MIND  127 

receptors  is  inhibited  save  from  those  of  the 
sense  of  hearing.  The  instructions,  i.  e.,  the 
suggestions,  are  made  orally  by  the  operator1; 
all  other  avenues  of  contact  with  the  outside 
world  are  for  the  time  being  closed.  The  train 
of  neurone  activity,  therefore,  which  is  set  in 
motion  by  the  suggestions  of  the  operator 
pursues  its  way  unchecked,  uncorrected,  for 
the  impressions  ordinarily  received  through 
vision  or  the  other  senses  cannot  gain  access 
to  the  train  of  neurone  activity,  the  field  of 
consciousness.  That  under  such  circumstances 
the  subject  should  prove  to  be  exceedingly 
susceptible  to  the  suggestions  of  the  operator 
is  not  surprising;  even  when  the  suggestions 
are  in  crass  contradiction  with  the  situation 
in  which  the  subject  happens  to  be  placed 
and  with  his  previous  experiences. 

The  patient  suffering  from  hysteria  while 
not  in  any  sense  asleep,  as  in  hypnosis,  yet 
resembles  the  hypnotized  subject  in  being 
abnormally  susceptible  to  suggestion.  Both 
Charcot  and  Gilles  de  la  Tourette  long  ago 
stressed  this  factor  in  their  descriptions  of 
hysteria.    It  was  Babinski,  however,  who  espe- 

1  Except,  of  course,  in  special  instances. 


128  THE  PHYSIOLOGY  OF  MIND 

cially  pointed  out  the  fact  that  the  symptoms 
have  their  origin  in  suggestions  that  may  arise 
from  causes  within  as  well  as  from  causes  with- 
out the  patient.  Especially  instructive  also 
were  the  facts  which  Babinski  presented  in 
regard  to  the  production  of  special  symptoms 
by  the  medical  examination  itself.  He  pointed 
out,  for  instance,  that  the  reason  hysterical 
hemianesthesia  predominates  on  the  left  side 
of  the  body  is  because  the  physician,  being 
usually  right-handed,  has  the  brush  or  sesthesi- 
ometer  in  his  right  hand,  and,  facing  the  patient 
and  asking  the  usual  questions,  he  naturally 
tests  the  left  side  of  the  patient's  body  first, 
thus  suggesting  the  very  anaesthesia  he  is  try- 
ing to  discover.  Similar  facts  obtain  in  regard 
to  the  induction  of  other  sensory  losses  and 
other  symptoms.  The  fact,  however,  of  great- 
est importance  is  that  the  same  or  similar 
procedures  may  be  practised  upon  normal  per- 
sons, but  without  the  slightest  result.  In  other 
words,  the  hysterical  subject  accepts  suggestions 
both  direct  and  indirect;  the  normal  person  re- 
pels them.  The  personality  of  the  hyster- 
ical patient  is  a  very  vulnerable  one.  Hysteria 
is,  indeed,  a  neuropathy  of  degeneracy.     Its 


THE  PHYSIOLOGY  OF  MIND  129 

symptoms  are  always  expressive  of  a  biological 
inferiority,  and,  in  keeping  with  this  fact,  it 
presents  a  large  element  of  heredity.  Charcot 
and  his  pupils  regarded  hysteria  as  always 
inherited;  all  other  causes  have  merely  the 
value  of  provocative  agents.  It  would  appear 
that,  as  in  hypnosis,  impacts  received  by  other 
receptors  than  those  which  serve  as  the  enter- 
ing avenue  of  the  suggestion,  fail  to  reach  or 
to  adequately  enter  the  train  of  transmission, 
the  field  of  consciousness.  That  when  the 
field  is  entered  as  a  result  of  psychotherapy  or 
other  cause,  or  when  the  suggestion  giving  rise 
to  the  symptom  ceases  to  be  operative,  the 
symptom  disappears,  is  a  matter  of  common 
experience.  It  is  not  my  intention  here  to 
consider  the  mechanism  of  hysteria  in  detail, 
such,  for  instance,  as  is  illustrated  by  the 
immediate  disappearance  of  the  hysteria  of 
litigation  when  the  claim  is  settled  or  other- 
wise disposed  of,  or,  of  cases  in  which  other 
"mental  compensation"  equally  powerful  oc- 
curs; for  this  would  take  us  too  far  from  our 
subject. 

The  discussion  of  the  phenomena  of  hypnosis 
and  of  hysteria  leads  naturally  to  the  discus- 


130  THE  PHYSIOLOGY  OF  MIND 

sion  of  dreams;  the  latter,  it  should  be  added 
however,  may  be  entirely  normal  manifestations 
As  in  hypnosis  and  hysteria,  there  is  in  a  dream 
a  field  of  cortical  neurones  active  during  a  period 
in  which  impacts  received  by  the  special  sense 
and  perhaps  other  receptors  are  denied  access. 
A  field  of  cortical  activity,  a  "train  of  trans 
mission"    arising   during   sleep,    may   have   its 
origin   in   one   of   two    ways:    First,   transmis- 
sion of  impacts  into  the  telencephalon  by  way 
of  the  special  sense  receptors  being  suspended 
during  sleep,  transmission  can  only  arise  from 
impacts  received  from  the  viscera  or  from  the 
soma  generally;  i.  e.,  from  the  interoceptors  or 
proprioceptors.      Secondly,    it    is    exceedingly 
probable  that  a  train  of  transmission  may  be 
started  by  direct  stimulation  of  the  neurones 
by    substances    circulating    in    the    blood;    for 
example,    by    hormones    present    in    unusual 
amount  or  modified  in  character,  or  by  toxins 
resulting  from  overfatigue  or  introduced  from 
without.     The   neurones,   too,   as   a   result   of 
fatigue    or    other    cause,    may    be    abnormally 
irritable.    It  is  exceedingly  probable  that  toxins 
act  primarily  upon  the  terminals  of  the  den- 
drites and  end-tufts  of  the  axones,  i.  e.,  upon 


THE  PHYSIOLOGY  OF  MIND  131 

the  synapses.  It  can  readily  be  comprehended 
how  in  this  way  a  train  of  transmission,  a  field 
of  cortical  activity,  may  arise.  The  train  of 
transmission  no  matter  how  arising,  being  un- 
inhibited, i.  e.,  uncorrected,  by  impacts  received 
from  the  external  world,  now  diffuses  along 
pathways  of  least  resistance;  former  neurone 
combinations  are  re-formed,  many  former  ones 
are  compounded;  unusual  and  bizarre  combi- 
nations result. 

Considerations  such  as  the  above  lead  not 
unnaturally  to  a  consideration  of  states  of 
delirium  and  confusion.  Here  we  have  to  deal 
with  problems  of  infection,  intoxication,  and 
exhaustion;  and  doubtless  with  the  action  of 
toxins  and  poisons  directly  and  primarily  upon 
the  synapses  and  secondarily  upon  the  bodies 
of  the  neurones.  Irregularly  occurring,  con- 
stantly changing  combinations,  discharges  and 
retractions  appear  to  feature  the  conditions; 
more  active  and  pronounced  in  delirium;  de- 
layed, slower  in  confusion;  and  abolished  in 
stupor.  In  keeping  with  this  interpretation 
we  find  delirium  featured  by  hallucinations, 
illusions,  and  unsystematized,  fragmentary  de- 
lusions.    An  hallucination  is  doubtless  excited 


132  THE  PHYSIOLOGY  OF  MIND 

by  the  direct  action  of  the  toxin  on  the  neurones 
of  a  special  sense  receiving  area  of  the  cortex; 
quite  commonly  it  involves  the  auditory  or  the 
visual  area.  The  disturbance  forcing  itself 
into  the  train  of  neurone  activity  already 
existing  is  naturally  regarded  by  the  latter, 
the  "communal  consciousness"  (see  p.  96),  as 
something  coming  from  without,  and  the  noises, 
words,  or  phrases  heard  or  the  object  seen  are 
referred  to  the  outside  world.  That  in  delirium 
errors  of  perception  also  occur  is  not  surprising. 
An  illusion — excluding,  of  course,  errors  in  the 
receiving  apparatus,  the  special  sense  organ — 
is  due  to  a  faulty  combination  of  the  neurones 
of  the  cortex  in  response  to  the  impacts  received, 
or  to  an  imperfect  or  aberrant  correlation  (in- 
tegration) with  combinations  previously  formed ; 
thus  occur  mistakes  in  the  recognition  of  objects 
and  persons.  That  the  resulting  state  of  the 
communal  consciousness  should  be  one  of  con- 
fusion more  or  less  active  according  to  the 
intensity  of  the  disturbance  is  what  we  should 
under  the  circumstances  be  led  to  expect. 

It  is  one  of  the  essential  features  of  delirious 
and  confused  states  that  there  is  an  absence 
of  fixation  of  any  of  the  symptoms.    The  pic- 


THE  PHYSIOLOGY  OF  MIND  133 

ture  is  one  constantly  changing,  constantly 
varying;  in  an  active  delirium  the  picture 
changes  with  kaleidoscopic  suddenness;  in  con- 
fusion much  more  slowly;  while  in  stupor  the 
deadening  weight  of  intoxication  and  exhaus- 
tion abolish  all  manifestations  whatever. 

In  certain  mental  diseases  fixation,  on  the 
contrary,  sooner  or  later  makes  its  appear- 
ance. In  order  that  its  significance  may  be 
fully  appreciated  a  digression  will  be  necessary. 

There  is  a  group  of  mental  diseases  which 
have  their  beginnings  before  the  foundation 
of  the  organism  is  laid.  The  building  material 
is  imperfect,  poor  in  quality,  vitiated,  so  that 
the  resulting  structure  crumbles  and  gives  way 
under  its  own  strains.  Mental  symptoms  make 
their  appearance  relatively  early,  and  this 
caused  the  early  French  writers,  notably  Morel, 
to  speak  of  it  as  demence  precoce,  a  name  which 
Arnold  Pick  long  after  rendered  into  the  now 
generally  accepted  term  "dementia  prsecox." 
As  might  be  expected,  the  number  of  factors 
which  enter  into  the  impaired  heredity  of  the 
patients  is  exceedingly  large  and  varied,  e.  g., 
mental  and  nervous  disease,  syphilis,  alcoholism, 
criminality,  prostitution,   vagabondage,  eccen- 


134  THE  PHYSIOLOGY  OF  MIND 

tricity;  in  fact,  all  forms  of  degeneracy,  mis- 
fits, and  failures. 

Dementia  prsecox  is  essentially  an  affection 
of  endogenous  deterioration.  It  should  really 
be  spoken  of  in  the  plural,  as  the  insanities 
of  adolescence,  because  in  keeping  with  the 
many  and  varied  hereditary  factors  entering 
into  its  causation,  it  manifests  itself  in  many 
forms.  Long  ago  two  groups  were  isolated 
by  Kahlbaum,  which  he  termed  respectively 
* 'hebephrenia"  and  "catatonia,"  and  to  these 
Kraepelin  later  added  a  third,  "paranoid 
dementia."  Later  still  Kraepelin  distinguished 
ten  different  forms  instead  of  three,  but  in 
this  he  has  not  been  generally  followed;  and 
doubtless  largely  because,  as  Kraepelin  himself 
admits,  there  are  between  the  various  forms  so 
many  transitional  forms  that  they  cannot  be 
sharply  delimited.  For  practical  purposes  the 
segregation  into  hebephrenia,  catatonia,  and 
paranoid  dementia  is  quite  commonly  accepted. 
Hebephrenia  is  a  relatively  simple  form,  which 
occurs,  on  the  whole,  in  the  younger  individuals; 
catatonia  is  distinguished  more  especially  by 
the  addition  of  certain  motor  phenomena  and 
also  presents  slight  evidences  of  "systematiza- 


THE  PHYSIOLOGY  OF  MIND  135 

tion"  of  the  delusive  ideas,  and  occurs,  on 
the  average,  in  somewhat  older  patients.  Para- 
noid dementia  is  distinguished  by  a  more 
pronounced  systematization  and  occurs,  on  the 
average,  in  a  still  older  group.  That  many 
transitional  forms  are  met  with  need  hardly 
be  restated.1 

Space  and  the  objects  of  this  Addendum 
do  not  permit  of  a  consideration  of  the  symp- 
toms of  dementia  praecox.  Suffice  it  to  say 
that  the  known  facts  in  our  possession  point 
clearly  to  an  auto  toxic  state  and  exhaustion.2 
The  onset  of  symptoms  is  gradual,  usually 
bearing  the  character  of  a  confusion,  some- 
times with  varying  elements  of  systematiza- 
tion and,  let  us  repeat,  of  weakness  and  ex- 
haustion. That  a  progressive  deterioration  and 
a  final  dementia  should  ensue  seems  quite 
natural;  and  it  is  this  that  occurs  in  the  larger 
number  of  cases. 

1  Because  of  his  interpretation  of  dementia  praecox  as  a  cleavage  or 
fissuration  of  the  mental  functions,  Bleuler  invented  and  proposed  the 
name  "schizophrenia,"  which  he  believes  to  be  preferable  to  dementia 
praecox.  However,  cleavages  and  figurations  of  the  personality  are  not 
confined  to  dementia  praecox,  but  also  occur  in  other  forms  of  mental 
disease  as  well  as  in  the  neuroses.  Both  the  term  and  the  affection  lack 
the  specificity  that  would  justify  its  use. 

2  Dercum,  The  Story  of  Dementia  Praecox,  New  York  Med.  Jour., 
Aug.  12,  1916;  also  Clin.  Manual  of  Mental  Dis.,  p.  108. 


136  THE  PHYSIOLOGY  OF  MIND 

The  behavior  of  the  neurones,  their  synapses, 
and  cell  bodies,  in  confusion  we  have  already 
considered.  The  researches  of  Fauser  and 
others  point  among  other  things  to  the  ingress 
into  the  blood  of  an  abnormal  hormone  from 
the  sex  glands.  Together  with  this  we  have  a 
nerve  substance  inherently  defective  and  feeble 
in  resistance.  As  a  natural  result  there  is 
present,  in  addition  to  the  confusion,  a  more 
or  less  marked  adynamia  of  the  field  of  cortical 
activity,  the  train  of  transmission.  The  level, 
the  intensity,  of  the  metabolic  processes  of 
the  neurones  is  lowered.  In  keeping  with  this 
there  is  slowness  of  speech  and  poverty  of 
thought  which  eventuate  in  mutism,  in  fixed 
positions,  stereotypy,  automatism,  persevera- 
tion, verbigeration;  or  it  may  be  stupor.  The 
train  of  transmission  is  reduced  to  a  shallow, 
a  narrow,  a  monotonously  trickling  stream, 
which  may  for  a  time  cease  altogether.  Now 
and  anon,  tributary  currents  join  what  is  left 
of  the  main  stream,  but  they  do  so  irregularly, 
at  unusual  points,  and  at  variance  with  the 
orderly  sequence  of  neurone  combinations. 
While  the  cortex  is  adynamic  as  a  whole,  it 
may  happen  that  the  field  of  cortical  activity 


THE  PHYSIOLOGY  OF  MIND  137 

is  more  greatly  reduced  than  other  portions. 
Under  normal  conditions  the  train  of  trans- 
mission, as  already  pointed  out,  diffuses,  dis- 
charges into  other  and  still  inactive  areas. 
However,  if  the  level  of  the  active  field  is 
greatly  diminished  and  other  portions  of  the 
cortex  become,  as  a  result  of  the  toxic  causes 
at  work,  spontaneously  active,  and  if  they 
possess  relatively  greater  dynamic  power,  the 
direction  of  the  diffusion  may  be  reversed  and 
these  new  activities  may  flow  into  the  less 
resistant  field.  It  is  not  necessary  to  suppose 
that  they  represent  "complexes"  that  have 
been  "repressed,"  to  use  the  language  of  the 
Freudians.  They  may,  of  course,  represent  a 
variety  of  things;  on  the  one  hand,  "wishes" 
and  things  desired,  and,  on  the  other,  things 
of  which  the  patient  stands  in  fear  and  dread; 
but  not  necessarily  either. 

We  have  already  traced  the  origin  of  a  hal- 
lucination, e.  g.,  of  hearing,  and  how  it  breaks 
into  the  train  of  transmission  and  how  it  is 
naturally  regarded  by  the  already  existing 
communal  consciousness  as  something  coming 
from  without.  In  a  similar  manner,  other  groups 
of   neurone   combinations  may,  as  a   result  of 


138  THE  PHYSIOLOGY  OF  MIND 

their  greater  dynamic  level,  diffuse  their  energy 
into  the  less  active  field.  That  phenomena  of 
cleavages  and  figurations  of  the  personality 
should  under  these  circumstances  result  is 
what  might  be  expected,  but  this  is  no  reason, 
as  has  already  been  pointed  out,  for  giving  to 
dementia  prsecox  the  specific  name  of  schizo- 
phrenia. 


Let  us  return  now  to  a  consideration  of  fixa- 
tion which  in  certain  mental  diseases  sooner 
or  later  makes  its  appearance.  We  have  seen 
how  in  delirium  and  confusion  there  occurs 
an  ever-changing  and  ever-varying  combina- 
tion among  the  neurones.  Synaptic  relations 
are  continuously  and  irregularly  made  and 
broken.  We  have  seen,  also,  that  in  dementia 
prsecox,  especially  in  the  younger  group,  the 
mental  picture  is  that  of  a  confusion,  but  that 
in  the  older  groups  "systematization"  of  the 
delusive  ideas  may  in  some  degree  be  present. 
By  systematization  is  meant  the  arrangement 
of  the  ideas  into  logical  sequence;  in  other 
words,  a  systematized  delusion  is  one  which  has 
a  logical  structure.    Now,  it  is  the  essence  of  an 


THE   PHYSIOLOGY  OF  MIND  139 

insane  delusion  that  the  person  holding  it  is 
incapable  of  accepting  evidence  concerning  it; 
i.  e.y  such  evidence  as  is  accepted  by  ordinary 
men  or  by  normal  minds.  This  can  only  mean 
that  the  neurone  combinations  concerned  in 
the  delusions  are  inaccessible.  It  is  entirely 
justifiable  to  assume  that  we  have  here  to  deal 
with  relations  between  neurones  which  recur 
with  such  ease  and  constancy  as  to  be  potentially 
fixed  in  character.  Inaccessibility  to  conflict- 
ing trains  of  neurone-  combinations  is  a  neces- 
sary result.  Any  impulse  approaching  the 
neurones  concerned  merely  results  in  the  re- 
formation of  the  old  combinations.  In  keep- 
ing with  this  we  meet  with  another  fact,  and 
that  is,  that  a  delusion  once  fixed  becomes 
permanent.  This  is  typically  illustrated  by  the 
history  of  the  various  forms  of  paranoia,  and, 
indeed,  in  general  terms,  it  may  be  stated  that 
the  appearance  of  systematized  delusions  in  a 
given  mental  case  is  always  an  unfavorable 
omen. 

The  application  of  the  physiological  prin- 
ciples developed  in  the  within  essay  to  melan- 
cholia and  mania  has  already  been  indicated 
(see   p.    111).      In  melancholia  the  retardation 


140  THE  PHYSIOLOGY  OF  MIND 

may  properly  be  ascribed  to  a  depressing  action 
upon  the  function  of  the  synapses  of  a  toxic 
hormone.  Possibly  to  this,  as  well  as  to  the 
general  action  of  the  toxin  upon  the  neurone 
bodies,  the  mental  suffering  is  to  be  attributed. 
It  would  seem  a  not  illogical  inference  to  regard 
the  painful  delusions  so  frequently  present, 
as  secondary  outgrowths,  as  the  explanations 
devised  by  the  patient  to  account  for  his  suffer- 
ings. At  all  events,  the  mental  distress  is  the 
essential  feature,  as  witness  the  cases  of  simple 
though  severe  melancholia  without  delusions. 

In  the  phase  of  mania,  as  already  pointed  out, 
the  resistance  of  the  synapses  is  greatly  dimin- 
ished; there  is  a  general  release  of  inhibition. 
It  would  seem  that  as  a  result  of  the  toxic 
hormone  or  other  cause  at  work,  the  neurones 
evolve  and  discharge  their  energy  with  unusual 
ease  and  that  the  latter  flows  with  lessened 
resistance  along  the  cell  processes.  The  patient 
is  expansive,  aggressive,  boisterous,  boastful, 
buoyant.  He  talks  incessantly  and  with  great 
rapidity;  he  rapidly  embraces  the  objects  and 
persons  in  a  room  in  the  scope  of  his  percep- 
tions, but  fastens  his  attention  upon  nothing. 
Illusions  of  objects   and  persons,   due  in   part 


THE   PHYSIOLOGY  OF  MIND  141 

to  the  fragmentary  and  imperfect  character 
of  the  perceptions  and  in  part  to  abnormal 
associations,  are  a  natural  consequence.  The 
associations  are  usually  striking,  unexpected; 
often  they  consist  of  meaningless  rhymes,  simi- 
larly sounding  words  or  syllables,  puns,  mere 
assonances.  There  is  an  enormous  increase 
in  the  flow  of  ideas;  but  the  latter  are  evanes- 
cent, fugacious,  unessential;  what  we  hear  is 
richer  in  words  than  in  ideas. 

The  expansion  and  the  enormously  increased 
association  of  mania  is  in  keeping  with 
heightened-  nervous  outflow,  the  increased 
energy  discharged  by  the  neurones.  Along 
with  this  are  the  motor  excitement  and  the 
unusual,  the  bizarre,  the  pathological  char- 
acter of  the  associations.  We  can  understand, 
perhaps,  why  the  nervous  overflow  should 
pass  along  unaccustomed  channels;  perhaps, 
also,  why  the  associations  lose  their  intimate, 
elaborate,  and  finer  qualities;  why  they  should 
become  coarse  or  relatively  so.  Normal  acts 
require  time,  and  probably  in  proportion  to  the 
amount  of  detail.  In  mania  the  discharges 
appear  to  be  diffused  en  masse  and  probably 
along  the  larger  pathways  in  which  the  least 


142  THE  PHYSIOLOGY  OF  MIND 

resistance  is  encountered.  Possibly  there  is 
here  an  explanation  of  the  coarseness  and 
superficiality  of  the  associations.  Finally,  it 
is  probable  that  fatigue  early  impairs  the 
synapses  upon  which  the  finer  adjustments 
depend,  so  that  as  the  case  progresses  coarse 
and  flaring  associations  alone  are  present. 

A  concluding  paragraph  upon  the  mental 
disturbances,  the  dementias,  which  ensue  upon 
the  gross  destructive  action  of  poisons,  such  as 
lead  and  alcohol,  and  upon  the  destruction-  of 
the  neurones  by  the  ravages  of  the  Spirochseta 
pallida  and  other  agents,  hardly  seems  neces- 
sary. The  action  of  these  is  obvious  and  the 
details  do  not  here  concern  us. 


INDEX 


Abstract  conceptions,  120 
thinking,  120 

Act  of  apperception,  100 
of  collocation,  100 

Activity,  train  of,  94 

Adaptation  in  metazoa  of  surface 
cell,  23,  42 
of  responses,  58,  62 

Addendum  on  pathological  physi- 
ology of  mind,  126 

Adequate  stimulus,  51 

Adjustor,  47 

Affects,  110 

Alimentary  canal,  48 

Altruism,  114 

Amino-acids  in  proteins,  19 

Amoeba,  reaction  to  environment, 
12 

Amoeboid  approach,  94 
movement  of  dermal  membrane 

of  sponges,  16 
transmission,  78 

Amoeboidism  of  cortical  neurones, 
63 
of  neurone,  71,  73 

Apperception,  99 

Association,  99 
paths,  53 
pathways,  61 

Attention,  105 

Automatic  character  of  spinal  re- 
sponses, 55 

Automatism,  acquired,  disappear- 


ance of  consciousness  in,  87 


Automatism  of  memory,  97 

of  response  in  approach  to  or 

withdrawal  from  foreign  bodies, 

51 
Avalanche  conduction,  81,  82 
Axone,  28,  71 
Azoulay,  65 

Babinski,  127,  128 
Bergson,  90 

Biological    endogenous    deteriora- 
tions, 134 

interpretation  of  mind,  122 
Blocking,  112 
Brain,  ear,  50,  107 

eye,  50,  107 

nose,  50,  107 

skin,  50,  107 

stem,  56 

visceral,  50 
Buchanan,  77 

Catatonia,  134 

Cell,  contractile,  differentiation  of, 
16 

intermediate,  differentiation  of, 
24 

metabolism,  13 

receiving,  differentiation  of,  23 

reducing  power  of,  14 

selecting  power  of,  13 
Centers,  cortical,  60 
Central  nervous  system,  segmental 

relations  of,  49 


143 


144 


INDEX 


Cephalic  extremity  and  special 
sense  receptors,  segmental  rela- 
tions of,  50 

Cerebral  cortex.  56,  57.  See  also 
Cortex. 

Charcot,  127,  129 

Chemical  impacts,  34 

received  by  surface  cell,  43 
sense,  51 

Chemotaxis,  68 

Ccelenterates,  pathways  for  trans- 
mission in,  21 
transmission  in  nerve  net  of,  29 

Collaterals,  28 

Collocation,  100 

Common  paths  of  transmission,  48, 
49,  78 

Communal  consciousness,  132 

Community  of  consciousness,  96 

Complexity  of  proteins,  19 

Composite  pictures,  120 

Concentration,  106 

Conceptions,  abstract,  120 
of  dimensions,  121 

Conduction,  avalanche>  81,  82 

Confusion,  131 

Conscious  and  unconscious  fields, 
relative  dynamic  power  of,  104 

Consciousness,  83 
communal,  132 
disappearance    of,    in    acquired 

automatisms,  87 
field  of,  93,  95,  101 
in  higher  vertebrates,  85 
in  lower  forms  of  life,  83 
in  lower  vertebrates,  84 
in  responses  of  adaptation  and 

adjustment,  88 
nature  of,  90 

relation  of  phenomena  of  cortical 
transmission  to,  89 


Contact    with    foreign    bodies    as 

stimuli,  34 
Contractile  cell,  differentiation  of, 

16 
Contractility  of  sponges,  16 
Cortex,  functions  of,  60 
relation  of  parts  of,  61 
responses   of,    and    relations   of 

neurones,  62,  63 
transmission       through,       phe- 
nomena of,  89 
Cortical  centers,  60 
dependencies,  59,  111 
neurones,  reactions  of,  75 

amoeboidism  of,  63 
transmission,  phenomena  of,  rela- 
tion to  consciousness,  89 


Dangers  of  abstract  thinking,  120 
de  la  Tourette,  126,  127 
Delirium,  131 
Delusions,  131 
Demence  precoce,  133 
Dementia,  paranoid,  134 

praecox,  133,  134 
Dendrites,  27,  71 
Dercum,   36,   63,    64,   65,   75,   94, 

135 
Dermal  membrane  of  sponges,  16 
Diffusion,  20 

Dimensions,  conception  of,  121 
Disappointment,  114 
Discharge  of  energy,  112  • 
Dreams,  130 

origin  of,  130 
Duval,  64 
Dynamic  levels,  105 

power,  relative,  of  conscious  and 
unconscious  fields,  104 

quality  of  memory,  97,  98 


INDEX 


145 


Ear,  36 

brain,  50,  107 

Edinger,  56 

Effector,  23,  25 

Egress,  pathways  of,  from  telen- 
cephalon, 59 

Einstein,  121,  124 

Electro-endosmotic  layer,  74 

Element  of  time,   significance  of, 
115 

Emotions,  110 

Endogenous  deteriorations,  biolog- 
ical, 134 

Energy,  discharge  of,  112 
release  of,  81 

Environment,  reaction  of  organism 
to,  12-19 

Expansion,  112 

Exteroceptive  sense,  44,  45 

Exteroceptors,  110 

Eye  brain,  50,  107 
spot,  37 

action  of,  37 

Fachner,  117 
Fauser,  136 

Field  of  consciousness,  93,  95,  101 
physiology  of,  102 
unconscious,  101 
Fischer,  Emil,  19 

Fixation,   appearance  and   signifi- 
cance of,  138 
Foreign  bodies,  contact  with,   as 
stimuli,  34 
impact  of,  reaction  of  proto- 
plasm to,  19 
Fourth  dimension,  121 
Freudians,  137 

Hallucinations,  131 

Heat,  impacts  of,  38 

10 


Heat,  influence  of,  on  activity  of 

protoplasm,  38 
Hebephrenia,  134 
Heredity  in  hysteria,  129 
Herrick,  39,  45,  50,  56,  61,  68,  69,77 
Higher   vertebrates,   consciousness 

in,  85 
Historical  data,  63 
Hodge,  95 
Hormones,  68 
Hypnosis,  126 
Hysteria,  63,  126 

heredity  in,  129 
Hysterical  paralysis,  theory  of,  63 

Idiot  savants,  98 
Illusions,  131 
Imagination,  104 
Impacts,  chemical,  34 

from  movements  and  coarse 
vibrations  in  surrounding  me- 
dium, 35 

groups  of,  52 

of  heat,  38 

of  light,  37 

physical,  special  sensations  from, 
107 

received  by  living  protoplasm,  34 
Incremental  stimulus,  72 
Ingress,  pathways  of,  to  telenceph- 
alon, 58 
Initial  stimulus,  72 
Initiative,  105 
Instincts,  97 
Intercalary  neurones,  31,  48 

effect  of,  32 
Intermediate    cell,    differentiation 

of,  24 
Internuncial  fibers,  52 

paths  of  transmission,  49 
Interoceptive  sense,  44 


146 


INDEX 


Interoceptors,  110 

Invertebrates,  nervous  system  of, 

24 
Iris,    response   to   direct   physical 

stimulation,  17 

Jelly-fishes,    nervous   apparatus 
in,  21 
pathways  for  transmission  in,  21 
Joy,  114 

Kahlbaum,  134 
Kappers,  69,  70,  71,  72,  74 
Knee  reflex,  32 
Knee-jerk,  32 
Kraepelin,  134 

Lateral  line  system,  36 

Lepine,  64 

Light,  impacts  of,  37 

influence  on  activity  of  proto- 
plasm, 37 
Limitations   of    possibilities,    only 
such  changes  as  protoplasm 
is  capable  of  receiving,  119 
these  changes  correspond  only 
imperfectly    to    changes    in 
outside  world,  119 
Loeb,  Jacques,  99 
Lower  forms  of  life,  consciousness 
in,  83 
vertebrates,  consciousness  in,  84 
Lugaro,  95 

Macula  acustica,  36 

Mammals,     fixed     responses     and 

consciousness  in,  86 
Mania,  112,  139 
Mauthner,  70 
Mechanism  of  response,  31 
Melancholia,  111,  139 


Memory,  97 

dynamic  quality  of,  97,  98 

its  automatism,  97 

pictures,  119,  120 
Mental  pain,  112 
Metabolism  of  cells,  13 
Metazoa,    adaptation    of    surface 

cell  in,  23,  42 
Mind,  11 

biological  interpretation  of,  122 

interpretation  of,  physical  con- 
ceptions in,  114 

pathological  physiology  of,  ad- 
dendum, 126 

phenomena  of,  11 
Morel,  133 
Motor  area,  109 

projection  fibers,  60 
Movement,  response  in,  19 
Movements  and  coarse  vibrations 

in  surrounding  medium,  impacts 

from,  35 
Multicellular  forms,  primitive  re- 
sponses of  movement  in,  15 
reactions  of  individual  cells  of, 
13 
Muscle    activity    independent    of 

nervous  influence,  17,  18 
Muscle-cell     in     pore    canals    of 

sponges,  23 
Music,  112 

Neo-encephalon,  57 

Nerve  net  of  ccelenterates,  trans- 
mission in,  29 

Nerve-cells,  27 
change  in  positions  of,  in  verte- 
brates, 69 
movement  of,  in  invertebrates,  66 
processes  of,  27 

Nervous  network,  structure  of,  26 


INDEX 


147 


Nervous  system,  central,  of  verte- 
brates, neurone  of,  27 
of  invertebrates,  24 
of  vertebrates,  24 
synaptic,  29 
differentiation  of,  27 
of  vertebrates,  30 
syncytic,  29 
Neurobiotactic  phenomenon,  71 
Neurobiotaxis,  69,  78 

principles  that  determine,  78 
Neuroblast,  67 
Neuroid  transmission,  21 
Neurone,  28 
amoeboidism  of,  71,  73 
changes  in,  81 
combinations,  59 
development  of,  67 
of    central    nervous    system    of 

vertebrates,  27 
origin  of,  67 
polarization  of,  70,  71 
relations,  variability  of,  133 
threshold,  78 
Neurones,  cortical,  amoeboidism  of, 
63 
intercalary,  31,  48 

effect  of,  32 
of  cortex,  relations  of,  62,  63 
relations  between,  100 
reforming  of  old  and  formation  of 
new  combinations  among,  103 
Nose  brain,  50 

Objections  to  Greek  word  V™*^ 
and  its  derivatives,  123 
to  Latin  word  spiritus  and  its 
derivatives,  123 
Olfactory  brain,  107 
impressions,  53 
lobes  in  fish,  51 


Organism,  response  by,  methods  of, 

47 
Originality,  104 
Otic  vesicle,  36,  38 
Otoliths,  88 

Pain,  110 

mental,  112 

physical  principles  of>  112 
Palseo-encephalon,  56 

role  of,  86 
Pallium,  r&le  of,  85 
Paralysis,  hysterical,  theory  of,  63 
Paranoid  dementia,  134 

states,  134,  135 
Parker,  15,  18,  20,  21,  22,  26,  27,  29 
Pathological  physiology  of   mind, 

addendum,  126 
Pathways,  association,  61 

of   ingress   to  and   egress  from 
telencephalon,  58 

of  transmission,  definite,  estab- 
lishment of,  48,  49 
old  and  new,  80 
primitive,  21 
Perception,  99 
Personal  equation,  115 
Phenomena  of  mind,  11 
Physical  conceptions  in  interpreta- 
tion of  mind,  114 
Pick,  Arnold,  133 
Pictures,  composite,  120 

memory,  119,  120 
Pleasure,  110 

physical  principles  of,  112 
Polarity  of  transmission,  30 
Polarization  of  neurone,  70,  71 
Pore  canal,  16 

epithelial  lining  of,  16 

of  sponges,  muscle-cell  in,  23 

membrane,  16 


148 


INDEX 


Precocious  dementias,  134 
Primitive   pathways   of   transmis- 
sion, 21 
responses  of  movement  in  multi- 
cellular forms,  15 
transmitting  apparatus,  position 
of,  24 
network,  structure  of,  26 
Proprioceptors,  110 
Protein,  complexity  of,  19 
Protoneurone,  24,  26 

function  of,  24 
Protoneurones,  66 
Protoplasm,  living,  capacity  of.  for 
transmission       of       motion 
through  its  own  substance, 
19 
changes    in    structure    of,    in 
response  to  changes  in  out- 
side world,  118 
function  of,  37 
impacts  received  by,  34 
influence  of  heat  on  activity 
of,  38 
of  light  on,  37 
limited  capacity  of,  for  recep- 
tion  of    incident   forces   of 
environment,  38.  39 
nature  of,  40 
reaction  to  medium,  35 
structure  of,  20,  40 
transparency  of,  37,  40,  42 
Pseudopod,    reaction    to    environ- 
ment, 12 
Pupin,  65 

PtABL-Riickard,  63,  64 
Race  memories,  97 
Ram<5n  y  Cajal,  65,  81 
Reactions    of    individual    cells    of 
multicellular  forms,  13,  14 


Reactions  of  organism  to  chemical 
impressions  of  environment, 
34 
to  environment,  12-19 
of  unicellular  forms,  12 
word,  77 
time,  76 
Receiving  cell,  differentiation  of,  23 
Receptor,  23,  25 
Receptors,  differentiation  of,  42 
limited  number  of,  39 
physical   character  of   function, 
42 
Reducing  power  of  cells,  14 
Reflex,  31 
knee,  32 
spinal,  32 
Regret,  114 
Release  of  energy,  81 
Response,   automatism  of,   in   ap- 
proach to  or  withdrawal  from 
foreign  bodies,  51 
by  organism,  methods  of,  47 
forms  of,  47 
in  movement,  19 
mechanism  of,  31 
Responses,  adaptable,  57 
adaptation  of,  5S,  62 
differentiation  of,  33 
exit  of,  59 
fixed,  56,  88 
invariable,  56 
of  adaptation   and  adjustment, 

consciousness  in,  88 
of  cortex  and  relations  of  neu- 
rones, 62,  63 
of  movement,  primitive,  in  multi- 
cellar  forms,  15 
origin  of,  58 

possibilities   of    adaptation   and 
adjustment  of,  62 


INDEX 


149 


Responses,  spinal,  automatic  char- 
acter of,  55 
variable,  56,  57 
in  higher  vertebrates,  57 

R6les  of  other  senses,  54 

Satisfaction,  114 
Schizophrenia,  135,  138 
Sea-anemones,   nervous  apparatus 
in,  21 

pathways  for  transmission  in,  22 
Segmental  apparatus,  56 

relations     of     central     nervous 
system,  49 
of     cephalic     extremity     and 

special  sense  receptors,  50 
of  telencephalon,  absence  of,  57 
Selecting  power  of  cells,  13 
Selective  action,  12 
Self,  sense  of,  96 
Sensation,  106,  109 

of  smell,  43 

of  taste,  43 
Sensations,  special,  from  physical 

impacts,  107 
Sense  cell,  23 

chemical,  51 

of  self,  96 

of  smell,  exteroceptive,  44,  45 

of  taste,  interoceptive,  44,  45 
Senses  of  smell  and  taste,  distinc- 
tion between,  44 

rules  of,  54 
Sensory  projection  fibers,  58 
Sentiency,  83,  106 
Sherrington,  44,  48,  71,  72,  73,  77, 

78,  110 
Significance  of  element  of  time,  115 
Skin  brain,  50,  107 
Sleep,  94,  95,  126 
Smell,  sensation  of,  43 


Smell,  sense  of,  44 

Sorrow,  114 

Sound,  transmission  of,  36 

Sphincter-like  action  in  canals  of 

sponges,  16 
Spinal  reflexes,  32 

responses,    automatic    character 
of,  55 
Sponges,  15 

amoeboid   movement   of   dermal 

membrane  of,  16 
contractility  of,  16 
dermal  membrane  of,  16 
muscle-cell  in  pore  canals  of,  28 
reaction  to  environment,  16 
sphincter-like  action  in  canals  of, 
16 
Stigma,  37  ■ 

action  of,  37 
Stimuli,  34 
Stimulus,  adequate,  51 

word,  77 
Stupor,  131 
Stylatella,  15,  20 

Surface    cell,    adaptation    of,    in 
metazoa,  23,  42 
chemical  impacts  received  by, 
43 
Synapse,  27,  28 
Synapses,  70 
Synaptic  delay,  71 
membrane,  75 
nervous  system,  29 

differentiation  of,  27 
of  vertebrates,  30 
resistance,  92 
Syncytic  nervous  system,  29 
Systematization,  138 

Taste,  sensation  of,  43 
sense  of,  44 


150 


INDEX 


Telencephalon,  57 
absence  of  segmental   relations 

of,  57 
pathways  of  ingress  to  and  egress 

from,  58 
role  of,  107 
Thought,  100 
Time,  element  of,  significance  of, 

115 
Tourette,  126,  127 
Train  of  activity,  94 
Transmission,  20 

common  paths  of,  48,  49 
in  nerve-net  of  ccelenterates,  29 
internuncial  paths  of,  49 
neuroid,  21 

of  impacts  through  organism,  47 
pathways  of,  definite  establish- 
ment of,  48   49 
old  and  new,  80 
polarity  of,  30 
primitive  pathways  of,  21 
principles  that  govern,  91 
through  cortex,  phenomena  of,  89 
Transmitting  apparatus,  primitive, 
position  of,  24 
in  more  complex  metazoa, 
24 
network,  primitive,  structure  of, 
26 


Transparency  of  protoplasm,   87, 
40,42 

Unconscious  and  conscious  fields, 
relative  dynamic  power  of,  104 
field,  101 

physiology  of,  102 

Unconsciousness,  94,  95 

Unicellular  forms,  reactions  of,  12 

Vertebrates,    higher,    conscious- 
ness in,  85 

lower,  consciousness  in,  84 

nervous  system  of,  24 

synaptic  nervous  system  of,  30 
Visceral  brain,  50 
Vision,  subdivisions  of,  110 
Visual  area,  108 

Waldeter,  28 

Weber,  117,  118 

Weber's  law,  significance  of,  116- 

118 
Wiedersheim,  66 
Will,  105 

power,  105,  106 
Wilson,  16 
Wishes,  137 
Wundt,  77,  117 


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